Aqueous dispersion for chemical mechanical polishing, chemical mechanical polishing process, production process of semiconductor device and material for preparing an aqueous dispersion for chemical mechanical polishing

ABSTRACT

Provided are an aqueous dispersion for chemical mechanical polishing, which planarizes a surface to be polished and has high shelf stability, a chemical mechanical polishing process excellent in selectivity when surfaces of different materials are polished, and a production process of a semiconductor device.  
     A first aqueous dispersion contains a water-soluble quaternary ammonium salt, an inorganic acid salt, abrasive grains and an aqueous medium. A second aqueous dispersion contains at least a water-soluble quaternary ammonium salt, another basic organic compound than the water-soluble quaternary ammonium salt, an inorganic acid salt, a water-soluble polymer, abrasive grains and an aqueous medium. The second aqueous dispersion is composed of a first aqueous dispersion material (I) obtained by mixing a water-soluble quaternary ammonium salt and an inorganic acid salt into an aqueous medium, and a second aqueous dispersion material (II) obtained by mixing a water-soluble polymer and another basic organic compound than the water-soluble quaternary ammonium salt into an aqueous medium. Abrasive grains are contained in at least one of the aqueous dispersion materials.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an aqueous dispersion forchemical mechanical polishing and a chemical mechanical polishingprocess making use of this dispersion. Further, the present inventionrelates particularly to an aqueous dispersion for chemical mechanicalpolishing that has high shelf stability, prevents deterioration withtime even in storage in a state of a high concentration, can provide apolished surface having excellent planarization and lessened surfacedefects by chemical mechanical polishing and is useful in production ofsemiconductor devices, a chemical mechanical polishing process excellentin polishing and removal selectivity making use of such a dispersion,and a production process of semiconductor devices.

[0003] 2. Description of the Background Art

[0004] With the increase of the degree of integration and the formationof multi-layer wiring in semiconductor devices, a technique of chemicalmechanical polishing is adopted for polishing of a film to be processed.This technique serves to remove an excess wiring material and form awiring by embedding a proper wiring material in grooves, holes or thelike of a desired pattern formed in a dielectrics on a process wafer andthen chemically and mechanically polishing the dielectrics.

[0005] Such a chemical mechanical polishing process is also applied toformation of capacitors, gate electrodes and the like in addition to theformation of wiring and utilized in specular polishing of a siliconwafer such as an SOI (silicon on insulator) substrate.

[0006] Objects to be polished by such a chemical mechanical polishingprocess include various films such as polysilicon films (polycrystallinesilicon films), monocrystalline silicon films, silicon oxide films,aluminum films, tungsten films and copper films.

[0007] In such a chemical mechanical polishing step, the object shouldbe naturally achieved by conducting polishing only for a standard timeof X/V (min) when an initial excess film of thickness X (Å), formed byembeding a wiring material in grooves or the like is polished at aremoval rate of V (Å/min). In an actual production step of semiconductordevices, however, over polishing exceeding the standard time, X/V (min)is carried out for the purpose of removing the wiring material remainingon other portions than the grooves or the like. “Dishing” that a portionof wiring becomes a concave form or “erosion” that a portion ofalternate wiring obtained by alternately forming a wiring portion and aninsulating portion becomes a concave form is caused by such overpolishing. These phenomena are not preferred in that yield ofsemiconductor devices is lowered.

[0008] Further, surface defects including so-called “scratches” ofabrased-like state, may be caused by polishing in some cases. Thisphenomenon may also lower yield of semiconductor devices like thedishing and erosion in some cases.

[0009] Various compositions such as aqueous dispersions for chemicalmechanical polishing for restraining such dishing and erosion, aqueousdispersions for chemical mechanical polishing for restraining thesurface defects such as scratches and aqueous dispersions for chemicalmechanical polishing having both properties in combination haveheretofore been proposed.

[0010] For example, it is disclosed that excellent surface planarizingability can be achieved by polishing a silicon wafer using a compositioncontaining silica and piperazine (Japanese Patent Application Laid-OpenNo. 154760/1993). However, piperazine that is an essential component ofthis disclosed composition is an objective substance to regulate theamount of discharge to environment, and so the use thereof becomes aproblem from the viewpoints of safety and influence on the environment.

[0011] In addition, compositions for polishing comprising at least oneabrasive grain selected from silicon dioxide, aluminum oxide, ceriumoxide, titanium oxide, silicon nitride, zirconium oxide and manganesedioxide and water, and additionally containing a basic organic compoundin a state dissolved are disclosed. It is described that by thesecompositions for polishing, a great removal rate is achieved, andoccurrence of surface defects on a polished surface can be lessened(see, for example, Japanese Patent Application Laid-Open No.321569/1998).

[0012] With requirement of the increase of the degree of integration andthe micronization in semiconductor devices, the micronization of awiring pitch and the formation of a thinner dielectrics make progress.By the micronization of the wiring pitch, a silicon oxide film and astopper layer composed of a nitride such as silicon nitride or titaniumnitride are also made fine. When the stopper layer is over polished,however, the intended function of the stopper layer cannot be fulfilled,and erosion or the like are caused, so that the function as asemiconductor substrate may be impaired in some cases.

[0013] In addition, the surface defects including scratches on apolished surface have such influence that electrical properties of adielectrics deposited thereon are deteriorated, and this influencebecomes greater by the formation of a thinner dielectrics.

[0014] When a surface to be polished having the above-described stopperlayer is polished with such a composition for polishing as describedabove, it is not easy to achieve both improvement of polishing andremoval selectivity as to the layer to be polished and the stopperlayer, and lessening of surface defects including scratches.

[0015] The term, “polishing and removal selectivity” as used hereinmeans properties that a high rate of polishing and removal is achievedas to a material to be polished, while the rate of polishing and removalis low as to other materials, and means properties that when a surfaceto be polished composed of, for example, at least 2 material ispolished, only one material to be polished can be polished with highefficiency without over polishing other materials to be polished. Morespecifically, the term, “polishing and removal selectivity as to a layerto be polished and a stopper layer” means properties that only the layerto be polished can be polished with high efficiency without overpolishing the stopper layer when both layer to be polished and stopperlayer are polished at the same time.

[0016] In order to solve the above-described problem, there have beenproposed compositions improved in the polishing and removal selectivityas to a polysilicon film and a silicon oxide film and compositionscontrolled in removal rate (hereinafter also referred to as “polishingrate”) of polishing a nitride.

[0017] For example, Japanese Patent Application Laid-Open No.321569/1998 discloses that the polishing rate of a silicon oxide filmcan be controlled by the above-described composition for polishing toincrease the polishing and removal selectivity as to a polysilicon filmand the silicon oxide film. However, it is not investigated to controlthe polishing rate of a nitride.

[0018] A composition for polishing comprising a tetramethylammoniumsalt, a base and hydrogen peroxide in combination is also disclosed. Itis described that by this composition, the polishing rate of a nitridecan be controlled to increase the polishing and removal selectivity asto both oxide and nitride (for example, Japanese Patent ApplicationLaid-Open No. 270401/1998). However, this composition is excellent inthe polishing and removal selectivity as to both oxide and nitride, butthe polishing and removal selectivity as to polysilicon that becomes amaterial of a gate electrode and a nitride and the polishing and removalselectivity as to polysilicon and silicon oxide are not investigated.

[0019] With respect to the above-described composition for polishing, inparticular, long-term stability in a high-concentration state thatconcentrations of respective components are higher than those in apolishing applicable state to be actually served for polishing is alsonot investigated, and the composition is assumed to be used withinseveral hours after preparation of the composition. Therefore, thiscomposition involves factors that cost is increased upon actual use,such as need of transporting and storing it in a state that theconcentrations of the components has been controlled as low as thoseupon its use.

SUMMARY OF THE INVENTION

[0020] The present invention has been made on the basis of the foregoingcircumstances and has as its first object the provision of an aqueousdispersion for chemical mechanical polishing, which is excellent insurface planarizing ability as dishing, erosion or the like is lessenedin a plarnarizing step of a surface to be polished by chemicalmechanical polishing, excellent in polishing and removal selectivity asto polysilicon and silicon oxide and polishing and removal selectivityas to polysilicon and a nitride, and excellent in long-term stabilityeven in a high-concentration state, a chemical mechanical polishingprocess using this composition, and a production process of asemiconductor device.

[0021] It is the second object of the present invention to provide anaqueous dispersion for chemical mechanical polishing, by which dishing,erosion or surface defects including scratches are restrained in aplarnarizing step of a surface to be polished by chemical mechanicalpolishing, and which is excellent in polishing and removal selectivityas to polysilicon and silicon oxide and polishing and removalselectivity as to polysilicon and a nitride, and excellent in long-termstability even in a high-concentration state, a chemical mechanicalpolishing process using this composition, and a production process of asemiconductor device.

[0022] According to the present invention, there is thus provided afirst aqueous dispersion (hereinafter also referred to as “firstslurry”) for chemical mechanical polishing obtained by mixing awater-soluble quaternary ammonium salt, an inorganic acid salt andabrasive grains into an aqueous medium.

[0023] According to the present invention, there is also provided asecond aqueous dispersion (hereinafter also referred to as “secondslurry”) for chemical mechanical polishing obtained by mixing at least awater-soluble quaternary ammonium salt, another basic organic compoundthan the water-soluble quaternary ammonium salt, an inorganic acid salt,a water-soluble polymer and abrasive grains into an aqueous medium.

[0024] According to the present invention, there is further provided amaterial for preparing an aqueous dispersion for chemical mechanicalpolishing, comprising a first aqueous dispersion material (I) obtainedby mixing at least a water-soluble quaternary ammonium salt and aninorganic acid salt into an aqueous medium, and a second aqueousdispersion material (II) obtained by mixing at least a water-solublepolymer and another basic organic compound than the water-solublequaternary ammonium salt into an aqueous medium, wherein abrasive grainsare mixed into at least one of the first aqueous dispersion material (I)and the second aqueous dispersion material (II), and the aqueousdispersion for chemical mechanical polishing is prepared by both of thefirst aqueous dispersion material (I) and the second aqueous dispersionmaterial (II).

[0025] According to the present invention, there is still furtherprovided a chemical mechanical polishing process comprising the step ofpolishing a surface to be polished with any of the aqueous dispersionsfor chemical mechanical polishing described above.

[0026] The chemical mechanical polishing process may further comprisesthe step of polishing the surface to be polished with another aqueousdispersion for chemical mechanical polishing than the above aqueousdispersion for chemical mechanical polishing.

[0027] According to the present invention, there is yet still furtherprovided a process for producing a semiconductor device wherein thesemiconductor device is produced by conducting the step of polishing asurface to be polished on a semiconductor substrate with any of theaqueous dispersions for chemical mechanical polishing described above.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The aqueous dispersions (hereinafter also referred to as“slurries” merely) for chemical mechanical polishing according to thepresent invention will hereinafter be described.

[0029] According to the present invention, there are fundamentallyprovided the first slurry and the second slurry.

[0030] <First Slurry>

[0031] The first slurry is obtained by mixing a water-soluble quaternaryammonium salt, an inorganic acid salt and abrasive grains into anaqueous medium.

[0032] The respective components making up the first slurry willhereinafter be described in detail.

[0033] The first slurry can be stored over a long period of time in ahigh-concentration state as described below. However, the preferredmixing proportions (hereinafter also referred to as “specific mixingproportions”) of the respective components described below are allvalues in a polishing applicable state to be served for polishing.

[0034] [1] Water-Soluble Quaternary Ammonium Salt:

[0035] The water-soluble quaternary ammonium salt is preferably acompound represented by the following formula (1):

[NR₄]⁺[OH]⁻  (1)

[0036] wherein R is an alkyl group having 1 to 4 carbon atoms.

[0037] Incidentally, 4 R groups may be the same or different from oneanother.

[0038] Specific examples thereof include compounds such astetramethylammonium hydroxide, tetraethylammonium hydroxide,tetrapropylammonium hydroxide, tetraisopropylammonium hydroxide,tetrabutylammonium hydroxide and tetraisobutylammonium hydroxide. Amongthese, tetramethylammonium hydroxide and tetraethylammonium hydroxideare particularly preferred.

[0039] The above-mentioned water-soluble quaternary ammonium salts maybe used either singly or in any combination thereof.

[0040] The mixing proportion of the water-soluble quaternary ammoniumsalt is preferably 0.005 to 5% by mass, more preferably 0.008 to 4% bymass, particularly preferably 0.01 to 3% by mass based on the total massof the first slurry. If the mixing proportion of the water-solublequaternary ammonium salt is lower than 0.005% by mass, a sufficientpolishing rate may not be achieved in some cases. It is not necessary tocontain the water-soluble quaternary ammonium salt in a proportionexceeding 5% by mass.

[0041] Incidentally, the water-soluble quaternary ammonium salt isdissolved in the resulting aqueous dispersion for chemical mechanicalpolishing, and a part thereof is contained as an ion.

[0042] [2] Inorganic Acid Salt:

[0043] Examples of the inorganic acid salt include the sodium salts,potassium salts, ammonium salts of inorganic acids such as hydrochloricacid, nitric acid, sulfuric acid, carbonic acid and phosphoric acid; andsodium salts, potassium salts and ammonium salts having ahydrogensulfate ion, hydrogencarbonate ion or hydrogenphosphate ion.Among these, ammonium salts are preferred, with ammonium carbonate,ammonium nitrate and ammonium sulfate being particularly preferred.These inorganic acid salts may be used either singly or in anycombination thereof.

[0044] The mixing proportion of the inorganic acid salt is preferably0.005 to 5% by mass, more preferably 0.008 to 4% by mass, particularlypreferably 0.01 to 3% by mass based on the total mass of the firstslurry.

[0045] If the mixing proportion of the inorganic acid salt is lower than0.005% by mass, the effect of controlling dishing and erosion, namely,the effect of lessening dishing and erosion may become insufficient insome cases. It is not necessary to contain the inorganic acid salt in aproportion exceeding 5% by mass.

[0046] [3] Abrasive Grains:

[0047] The abrasive grains include inorganic particles, organicparticles and composite particles.

[0048] As examples of the inorganic particles, may be mentionedparticles of silicon dioxide, aluminum oxide, cerium oxide, titaniumoxide, zirconium oxide, silicon nitride, manganese dioxide and the like.Among these, particles of silicon dioxide are preferred.

[0049] As specific examples of the silicon oxide particles, may bementioned fumed silica synthesized by a fumed process, in which siliconchloride or the like is reacted with oxygen and hydrogen in a vaporphase, colloidal silica synthesized by a sol-gel process, in which ametal alkoxide is hydrolyzed and condensed, and colloidal silicasynthesized by an inorganic colloid process, in which impurities areremoved by purification.

[0050] The colloidal silica synthesized by the sol-gel process orcolloid process is present in a state that primary particles haveassociated or aggregated in an aqueous medium, i.e., in a state ofsecondary particles, when the particle diameter thereof is relativelysmall. The inorganic particles in such a state preferably have anaverage particle diameter of 1 to 3,000 nm, more preferably 2 to 1,000nm in terms of primary particles.

[0051] The average particle diameter of the secondary particles ispreferably 5 to 5,000 nm, more preferably 5 to 3,000 nm, particularlypreferably 10 to 1,000 nm. If inorganic particles, the average particlediameter of the secondary particles of which is smaller than 5 nm, areused, the resulting aqueous dispersion for chemical mechanical polishingcannot achieve a sufficiently high polishing rate in some cases. On theother hand, with a slurry using inorganic particles, the averageparticle diameter of the secondary particles of which exceeds 5,000 nm,the prevention of dishing and erosion may become insufficient in somecases, and further, surface defects such as scratches may be liable tooccur.

[0052] The average particle diameter of the primary particles can becalculated out from the measurement of the specific surface area of theintended particles and observation through a transmission type electronmicroscope, and the like. The average particle diameter of the secondaryparticles can be determined by measurement by means of a laserscattering diffraction measuring device, or the like.

[0053] On the other hand, inorganic particles such as silica synthesizedby the fumed process are produced in the form of secondary particles,and it is very difficult to disperse them in a state of primaryparticles in an aqueous medium, and so such particles are present assecondary particles obtained by aggregation of primary particles.Accordingly, the inorganic particles formed of silica synthesized by thefumed process are sufficiently identified so far as the secondaryparticles thereof are defined.

[0054] In the inorganic particles such as silica synthesized by thefumed process, the average particle diameter of the secondary particlesthereof are preferably 10 to 10,000 nm, more preferably 20 to 7,000 nm,particularly preferably 50 to 5,000 nm. By using the inorganic particlescomposed of fumed silica, the average particle diameter of the secondaryparticles of which falls within this range, there can be provided aslurry which can achieve a high polishing rate, sufficiently preventsdishing and erosion and is high in stability.

[0055] As examples of the organic particles, may be mentioned polymerparticles respectively composed of (1) polystyrene and styrenecopolymers, (2) (meth)acrylic polymer and (meth)acrylic copolymers suchas polymethyl methacrylate, (3) polyvinyl chloride, polyacetal,saturated polyester, polyamide, polyimide, polycarbonate and phenoxyresins, and (4) polyolefins and olefin copolymers such as polyethylene,polypropylene, poly(1-butene) and poly(4-methyl-1-pentene), and besidesother thermoplastic resins.

[0056] These organic particles can be prepared by a method of grinding aresin obtained by an emulsion polymerization process, suspensionpolymerization process, emulsion dispersion polymerization process, bulkpolymerization process or the like, or other methods. The organicparticles may also be particles of a copolymer having a crosslinkedstructure obtained by causing a crosslinkable monomer such asdivinylbenzene or ethylene glycol dimethacrylate to coexist in theabove-described polymerization process.

[0057] The organic particles are preferably particles of a resinselected from (1) polystyrene and styrene copolymers and (2)(meth)acrylic polymer and (meth)acrylic copolymers such as polymethylmethacrylate among the resin mentioned above, and their copolymershaving a crosslinked structure.

[0058] In such organic particles as described above, almost all theparticles thereof are generally present as simple particles in theslurry. The average particle diameter of these organic particles ispreferably 10 to 5,000 nm, more preferably 15 to 3,000 nm, particularlypreferably 20 to 1,000 nm. By using the organic particles having anaverage particle diameter within this range, there can be provided anaqueous dispersion for chemical mechanical polishing which can achieve ahigh polishing rate, sufficiently prevents dishing and erosion and ishigh in stability.

[0059] In the present invention, as specific examples of the compositeparticles, may be mentioned inorganic organic composite particlesobtained by integrally combining organic particles with inorganicparticles, and modified particles obtained by bonding a modifyingsubstance to surfaces of organic particles.

[0060] The composite particles composed of the inorganic organiccomposite particles are those obtained by integrally combining organicparticles with inorganic particles to the extent that these particlesare not easily separated. No particular limitation is imposed on thekinds of these organic particles and inorganic particles. For example,the same organic particles and inorganic particles as mentioned abovemay be used.

[0061] No particular limitation is also imposed on the specificstructure of the composite particles. For example, those obtained bycombining the organic particles composed of polymer particles with theinorganic particles by a proper method are preferably used.

[0062] More specifically, particles in a state that organic particlesand inorganic particles, polarity of zeta potential of which aredifferent from each other, have been combined by electrostatic force in,for example, an aqueous medium may be used as the composite particles.

[0063] The zeta potential of the organic particles is often negative inthe whole pH range or a wide pH range exclusive of a low pH range. Inparticular, organic particles composed of a polymer having a carboxylgroup, sulfonic group or the like surely have a negative zeta potential,and organic particles composed of a polymer having an amino group or thelike have a positive zeta potential in a specific pH range. On the otherhand, the zeta potential of the inorganic particles have high dependencyon pH, and some inorganic particles have an isoelectric point, at whicha zeta potential is zero, at a characteristic pH. In such inorganicparticles, the polarity of the zeta potential thereof is reversed aboveand below this point.

[0064] From the above-described fact, a specific kind of organicparticles are combined with a specific kind of inorganic particles, andboth particles are mixed in such a pH range that their zeta potentialsbecome reverse polarities to each other, whereby inorganic organiccomposite particles in a state that such organic particles and inorganicparticles have been integrally combined by electrostatic force can beobtained. Even when the zeta potentials of organic particles andinorganic particles mixed have the same polarity upon mixing, inorganicorganic composite particles in a state that the organic particles andinorganic particles have been integrally combined can also be obtainedby changing the pH after the mixing to create a state that the zetapotentials thereof become reverse polarities to each other.

[0065] In the present invention, the composite particles may be modifiedorganic particles of a state that a proper modifying substance has beenbonded to the surfaces of organic particle composed of, for example,polymer particles. As examples of the polymer particles, may bementioned particles of polystyrene and polymethyl methacrylate. Thepolymer particles, to which the modifying substance has been bonded, canbe obtained by, for example, a method in which a reactive material formodifying substance, such as an alkoxysilane, aluminum alkoxide ortitanium alkoxide, is polycondensed in the presence of the polymerparticles to form the modifying substance on the surfaces of the polymerparticles.

[0066] When the material for the modifying substance is an alkoxysilane,modified organic particles of a state that the polymer particles havingpolysiloxane on the surfaces thereof can be obtained. When the materialfor the modifying substance is an aluminum alkoxide or titanium alkoxideon the other hand, modified organic particles having atomic groupcontaining an aluminum or titanium atom can be obtained. In the methoddescribed above, the surfaces of the polymer particles may also betreated with a silane coupling agent or the like.

[0067] In the present invention, the composite particles may also beinorganic organic composite particles combined by bonding inorganicparticles such as silica particles or alumina particles to the surfacesof organic particles composed of proper polymer particles. In this case,the inorganic particles may be bonded in a form physically held to abonding component such as polysiloxane on the surfaces of the polymerparticles or be chemically bonded by a functional group such as ahydroxyl group existing on the surfaces of the polymer particles.

[0068] Those of a state that the inorganic organic composite particlesintegrally bonded by electrostatic force as described above have beenmodified by a modifying substance by a polycondensation reaction of, forexample, an alkoxysilane, aluminum alkoxide, titanium alkoxide or thelike in the presence of such inorganic organic composite particles canalso be used as the composite particles.

[0069] When the composite particles are composed of the inorganicorganic composite particles, such composite particles exist in any ofthe following States (1) to (3) according to the particle diameters andcomponent proportions of the respective organic particles and inorganicparticles forming the composite particles or in a state where more thanone of the states are present in combination.

[0070] State (1): a state that the inorganic particles have adhered asshell particles to the surfaces of core particles composed of theorganic particles.

[0071] State (2): a state that the organic particles have adhered asshell particles to the surfaces of core particles composed of theinorganic particles.

[0072] State (3): a state that the organic particle and inorganicparticles have aggregated to each other without forming a clearcore-shell structure.

[0073] Among the above-described states, State (1) or (3) is preferred.

[0074] In each of States (1) to (3), the inorganic particles may be inany state of primary particles and secondary particles, or bothparticles may be mixed.

[0075] With respect to the component proportions of the inorganicparticles and organic particles forming the inorganic organic compositeparticles, the proportion of the inorganic particles is preferably 1 to2,000 parts by mass, more preferably 10 to 1,000 parts by mass per 100parts by mass of the organic particles.

[0076] In the present invention, the average particle diameter of thecomposite particles is preferably 20 to 20,000 nm, more preferably 50 to10,000 nm, particularly preferably 50 to 5,000 nm.

[0077] By containing the composite particles satisfying theabove-described conditions, there can be provided a slurry which canachieve a high polishing rate, sufficiently prevents dishing and erosionand is high in stability.

[0078] The mixing proportion of the abrasive grains may be controlled topreferably 0.01 to 10% by mass, more preferably 0.03 to 8% by mass,particularly preferably 0.05 to 5% by mass based on the total mass ofthe first slurry. If the mixing proportion of the abrasive grains islower than 0.01% by mass, the resulting slurry cannot achieve sufficientpolishing rate. If the mixing proportion exceeds 10% by mass on theother hand, the resulting slurry becomes high cost and may bedeteriorated in shelf stability in some cases.

[0079] [4] Aqueous Medium:

[0080] The first slurry is obtained by mixing the water-solublequaternary ammonium salt, inorganic acid salt and abrasive grains asdescribed above, and components optionally contained into an aqueousmedium to disperse them in the aqueous medium. As the aqueous medium,may be used water, a mixed medium comprising water and a water-solublealcohol in an amount or proportion within a range not impairing thepolishing performance, or the like. However, water is particularlypreferred.

[0081] [5] Other Components:

[0082] The first slurry is obtained by mixing the water-solublequaternary ammonium salt, inorganic acid salt and abrasive grains intothe aqueous medium as described above and may contain additives such asorganic acids or salts thereof, oxidizing agents and/or surfactants asneeded in addition to the above-described components. A water-solublepolymer may also be contained.

[0083] Specific examples of the organic acids include formic acid,acetic acid, propionic acid, p-toluenesulfonic acid, isoprenesulfonicacid, gluconic acid, lactic acid, citric acid, tartaric acid, malicacid, glycolic acid, adipic acid, malonic acid, oxalic acid, succinicacid, fumaric acid, maleic acid and phthalic acid, and besides alanine,glycine, aspartic acid and glycylglycine that are amino acids.

[0084] The salts of the organic acids include alkali metal salts such aspotassium salts and ammonium salts of the above-mentioned organic acids.

[0085] These organic acids or the salts thereof may be used eithersingly or in any combination thereof. Alternatively, the organic acidsand salts may be used in combination.

[0086] The mixing proportion of the organic acid or the salt thereof maybe controlled to preferably at most 1% by mass, more preferably at most0.5% by mass based on the total mass of the first slurry.

[0087] The mixing proportion of the organic acid is controlled withinthe above-described range, whereby the resulting slurry can achievesufficient polishing characteristics and becomes stable.

[0088] Specific examples of the oxidizing agents include hydrogenperoxide, organic peroxides such as peracetic acid, perbenzoic acid andtert-butyl hydroperoxide, nitric compounds such as nitric acid and ironnitrate, perhalogenic compounds such as perchloric acid, persulfatessuch as ammonium persulfate, polyvalent metal salts such as iron nitrateand cerium ammonium nitrate, and heteropoly-acids such as silicotungsticacid, phosphotungstic acid, silicomolybdic acid and phosphomolybdicacid. Among these, hydrogen peroxide and organic peroxides, in which nometal element is contained, and decomposition products thereof areharmless, are preferred. By containing these oxidizing agents, apolishing rate can be greatly improved, in particular, when a metal filmsuch as a film to be worked that is formed on a wafer is polished.

[0089] These oxidizing agents may be used either singly or in anycombination thereof.

[0090] The mixing proportion of the oxidizing agent may be controlled toat most 15% by mass, preferably 0.001 to 15% by mass, more preferably0.03 to 10% by mass, particularly preferably 0.01 to 8% by mass based onthe total mass of the first slurry.

[0091] The mixing proportion of the oxidizing agent is controlled withinthe above-described range, whereby the resulting slurry can achieve asufficiently high polishing rate.

[0092] As the surfactants, may be mentioned cationic surfactants,anionic surfactants, nonionic surfactants and amphoteric surfactants.

[0093] Among these, the anionic surfactants and nonionic surfactants arepreferred.

[0094] Specific examples of the cationic surfactants include aliphaticamine salts and aliphatic ammonium salts.

[0095] Specific examples of the anionic surfactants include carboxylicacid salts such as fatty acid soap and alkyl ether carboxylic acidsalts, sulfonic acid salts such as alkyl benzene sulfonic acid salts,alkyl naphthalene sulfonic acid salts and α-olefinsulfonic acid salts,sulfate salts such as higher alcohol sulfate salts and alkyl ethersulfate salts, and phosphate salts such as alkyl phosphate salts.

[0096] Specific examples of the nonionic surfactants include ether typesurfactants such as polyoxyethylene alkyl ethers, ether ester typesurfactants such as polyoxyethylene ethers of glycerol esters, estertype surfactants such as polyethylene glycol fatty acid esters, glycerolesters and sorbitan esters, acetylene glycol and ethylene oxide adductsthereof, and acetylene alcohol.

[0097] Specific examples of the amphoteric surfactants includealkylbetaines and amine oxides.

[0098] These surfactants may be used either singly or in any combinationthereof. Different kinds of surfactants may also be used in combination.

[0099] The mixing proportion of the surfactant may preferably becontrolled to at most 1% by mass, more preferably at most 0.5% by massbased on the total mass of the first slurry.

[0100] The mixing proportion of the surfactant is controlled within theabove range, whereby the resulting slurry can achieve sufficientpolishing characteristics and becomes stable.

[0101] Specific examples of the water-soluble polymer include cellulose,carboxymethyl cellulose, hydroxyethyl cellulose, polyethylene glycol,polyethyleneimine, and polyacrylic acid and salts thereof.

[0102] These water-soluble polymers may be used either singly or in anycombination thereof.

[0103] The mixing proportion of the water-soluble polymer may becontrolled to preferably at most 1% by mass, more preferably at most0.5% by mass based on the total mass of the first slurry.

[0104] The mixing proportion of the water-soluble polymer is controlledwithin the above range, whereby the resulting slurry can achievesufficient polishing characteristics and becomes stable.

[0105] These additives, which may be optionally contained as needed, maybe mixed upon preparation of the first slurry, or may also be mixed in asupply line of the first slurry or on a polishing table upon thepractice of the chemical mechanical polishing step by separatelypreparing an aqueous solution thereof.

[0106] The preferable pH of the first slurry varies according to thekind of a film to be polished. For example, when a monocrystallinesilicon film or polysilicon film is polished, the preferable pH range is7 to 13, more preferably 9 to 12. If the pH is lower than 7, sufficientpolishing performance may not be achieved in some cases. If the pHexceeds 13 on the other hand, the stability of the slurry itself may bedeteriorated in some cases. It is not preferable for the first slurry tohave such a too low or high pH.

[0107] In order to adjust the pH of the first slurry, an acid or basemay be used. Examples of usable bases include potassium hydroxide andammonia.

[0108] As a film to be polished with the first slurry, is preferred asilicon type film. Specific examples thereof include amorphous siliconfilms, monocrystalline silicon films, polysilicon films, silicon nitridefilms and the like.

[0109] When the silicon type film is polysilicon film or amorphoussilicon film, arsenic and phosphorus or the like may be doped intopolysilicon and/or amorphous silicon, respectively forming these films.

[0110] When chemical mechanical polishing is conducted with the firstslurry, the polishing is conducted with the slurry, in which the mixingproportions of the respective components of the water-soluble quaternaryammonium salt, inorganic acid salt and abrasive grains and theoptionally contained components fall within the ranges of the specificmixing proportions as described above. The first slurry used in thispolishing may be prepared by mixing the respective components in amountscorresponding to the specific mixing proportions. Alternatively, ahigh-concentration product of a state that concentrations of therespective components are higher than the specific mixing proportions ina polishing applicable state to be actually served for polishing may beprepared in advance, and this high-concentration product may be dilutedwith water or the like upon the polishing in such a manner that themixing proportions of the respective components amount to the specificmixing proportions.

[0111] The high-concentration product of the first slurry is obtained bymixing the respective components in such a manner that the range of aratio regarding to the mixing proportions of the respective componentsequals to the range of a ratio regarding to the specific mixingproportions, and the mixing proportions of the respective components atthis time are preferably such that the water-soluble quaternary ammoniumsalt is at most 10% by mass, the inorganic acid salt is at most 10% bymass, and the abrasive grains are at most 20% by mass, all based on thetotal mass of the high-concentration product.

[0112] The first slurry can exhibit the initial polishing performance inthe case where it is used, by diluting it as required, in a chemicalmechanical polishing step after stored for a long period of time evenwhen the slurry is either a slurry in a polishing applicable stateprepared by mixing the respective components in amounts corresponding tothe specific mixing proportions or a slurry in a high-concentrationstate.

[0113] For example, the first slurry can exhibit the initial performanceeven when it is used in the polishing step after it is stored at 40° C.for 30 days or for 90 days in a high-concentration state and diluted.

[0114] Incidentally, the term “initial” means elapsed time of severalhours (1 to 5 hours) soon after the mixing of the respective components.

[0115] [6] Chemical Mechanical Polishing of Surface to be Polished:

[0116] The first chemical mechanical polishing process according to thepresent invention comprises the step of polishing a surface to bepolished with the first slurry.

[0117] When chemical mechanical polishing of the surface to be polishedis carried out with the first slurry, a commercially available chemicalmechanical polishing apparatus such as Model “EPO-112” or Model“EPO-222”, manufactured by Ebara Corporation; Model “Mirra”,manufactured by Applied Materials Inc.; or the like can be used toconduct the polishing under prescribed polishing conditions.

[0118] According to an embodiment of the first chemical mechanicalpolishing process of the present invention, for example, a grooveportion is formed on a semiconductor substrate, a polysilicon film isformed on the whole surface of the semiconductor substrate includingthis groove, the polysilicon film is then subjected to a polishingtreatment using such a chemical mechanical polishing apparatus asdescribed above and the first slurry to remove other portions of thepolysilicon film than a portion buried in the groove portion, whereby aburied groove having excellent surface characteristics and composed ofthe polysilicon can be formed in the groove portion formed on thesemiconductor substrate.

[0119] According to another embodiment, a silicon oxide film is formedon a semiconductor substrate, and a groove portion is additionallyformed on the resultant stacked film. After a polysilicon film isfurther deposited on the groove portion formed on the stacked film, thedeposited polysilicon film is subjected to a polishing treatment usingthe silicon oxide film as a stopper layer, and a surface exposed by thispolishing treatment is treated as a surface to be polished to conduct apolishing treatment using, for example, the above-described chemicalmechanical polishing apparatus and the first slurry, whereby a buriedgroove having excellent surface characteristics and composed of thepolysilicon can be formed in the groove portion formed on the stackedfilm obtained by stacking the silicon oxide film on the semiconductorsubstrate because the first slurry has excellent polishing and removalselectivity as to the polysilicon film and the silicon oxide film. Inthis embodiment, even when a polishing treatment is conducted in thesame manner as in said embodiment except that a nitride film is formedin place of the silicon oxide film, and this nitride film is used as astopper layer, a buried groove having excellent surface characteristicsand composed of the polysilicon can be formed in the groove portionformed on the stacked film obtained by stacking the nitride film on thesemiconductor substrate because the first slurry has excellent polishingand removal selectivity as to the polysilicon film and the nitride film.

[0120] According to a further embodiment, a monocrystalline silicon filmcan be polished in a specular state using the above-described chemicalmechanical polishing apparatus and the first slurry.

[0121] According to a still further embodiment, a groove portion isformed on a semiconductor substrate, a wiring material film is formed onthe whole surface of the semiconductor substrate including this groove,and a chemical mechanical polishing treatment is then conducted usingthe above-described chemical mechanical polishing apparatus and thefirst slurry to remove other portions of the wiring material film than aportion buried in the groove portion, whereby a buried wiring havingexcellent surface characteristics can be formed in the groove portionformed on the semiconductor substrate.

[0122] The evaluation of each of the polishing and removal selectivityas to the polysilicon film and the silicon oxide film and the polishingand removal selectivity as to the polysilicon film and the nitride filmcan be made by polishing the respective films to be polished under thesame conditions to compare them, specifically, by determining a ratio ofpolishing rates between both films. The term, “the same conditions”means that a polishing apparatus of a specific model is used, and therotating speeds of the platen and head thereof, polishing pressure,polishing time, the kind of a polishing pad used and a feeding amount ofthe aqueous dispersion for chemical mechanical polishing per unit timeare made the same. The “ratio of polishing rates” can be calculated outfrom the value of respective polishing rates of the polysilicon film,silicon oxide film and nitride film when these films are separatelypolished under the same conditions.

[0123] Examples of the nitride film include a silicon nitride film, atitanium nitride film and tantalum nitride film.

[0124] In the first chemical mechanical polishing process of the presentinvention, a first specific polishing rate ratio represented by a ratioof the polishing rate of a polysilicon film to the polishing rate of asilicon oxide film in the case where the silicon oxide film andpolysilicon film are polished under the same conditions may becontrolled to at least 30, preferably at least 100, particularlypreferably at least 300. Alternatively, a second specific polishing rateratio represented by a ratio of the polishing rate of a polysilicon filmto the polishing rate of a nitride film in the case where the nitridefilm and polysilicon film are polished under the same conditions may becontrolled to at least 50, preferably at least 100, particularlypreferably at least 300.

[0125] After completion of the polishing treatment, the abrasive grainsremaining on the polished surface are preferably removed. The removal ofthe abrasive grains can be conducted by an ordinary cleaning method. Forexample, cleaning is conducted with an alkaline washing solutioncontaining ammonia, hydrogen peroxide and water in a mass ratio of about1:1:5 respectively after brush-scrubbing, whereby the abrasive grainsadhered to the surface polished can be removed.

[0126] In order to remove impurity metal species adsorbed on thepolished surface, cleaning may be conducted with a washing solutioncomposed of, for example, an aqueous solution of citric acid, a mixedaqueous solution of hydrofluoric acid and citric acid or a mixed aqueoussolution of hydrofluoric acid and ethylenediamine-tetraacetic acid(EDTA).

[0127] When the abrasive grains are composed of organic particles alone,the polished surface may also be heated to a high temperature in thepresence of oxygen, thereby burning and removing the organic particleson the polished surface. As examples of a specific method of burning,may be mentioned an ashing treatment by causing oxygen plasma to act orby supplying oxygen radical by down flow. By this method, the organicparticles remaining on the polished surface can be easily removed.

[0128] [7] Production Process of Semiconductor Device:

[0129] The first production process of a semiconductor device accordingto the present invention is a process for producing a semiconductordevice using the first slurry. The term, “semiconductor device” widelymeans a polished wafer, various devices equipped with this wafer orholding the wafer and various devices equipped with a substrate producedfrom this wafer (i.e., various devices of which this substrate iscombined with).

[0130] <Second Slurry>

[0131] The second slurry is obtained by mixing at least a water-solublequaternary ammonium salt, another basic organic compound than thewater-soluble quaternary ammonium salt, an inorganic acid salt, awater-soluble polymer and abrasive grains into an aqueous medium.

[0132] The second slurry will hereinafter be described in detail.

[0133] The second slurry is provided in the form of an allcomponents-containing type slurry containing at least the water-solublequaternary ammonium salt, another basic organic compound than thewater-soluble quaternary ammonium salt, the inorganic acid salt, thewater-soluble polymer, the abrasive grains and the aqueous medium or atwo-liquid mixed type slurry composed of a material for preparing anaqueous dispersion for chemical mechanical polishing.

[0134] The material for preparing an aqueous dispersion for chemicalmechanical polishing comprises a first aqueous dispersion material (I)obtained by mixing at least a water-soluble quaternary ammonium salt andan inorganic acid salt into an aqueous medium, and a second aqueousdispersion material (II) obtained by mixing at least a water-solublepolymer and another basic organic compound than the water-solublequaternary ammonium salt into an aqueous medium, wherein abrasive grainsare mixed into at least one of the first aqueous dispersion material (I)and the second aqueous dispersion material (II), and the aqueousdispersion for chemical mechanical polishing is prepared by both of thefirst aqueous dispersion material (I) and the second aqueous dispersionmaterial (II).

[0135] The second slurry may be stored over a long period of time in ahigh-concentration state as described below. However, the preferredspecific mixing proportions of the respective components described beloware all values in a polishing applicable state to be served forpolishing.

[0136] [1] Water-Soluble Quaternary Ammonium Salt and Another BasicOrganic Compound than the Water-Soluble Quaternary Ammonium Salt:

[0137] The all components-containing type slurry contains bothwater-soluble quaternary ammonium salt and another basic organiccompound than the water-soluble quaternary ammonium salt.

[0138] In the two-liquid mixed type slurry, the water-soluble quaternaryammonium salt is contained in the first aqueous dispersion material (I),while at least another basic organic compound than the water-solublequaternary ammonium salt is contained in the second aqueous dispersionmaterial (II). This second aqueous dispersion material (II) may furthercontain the water-soluble quaternary ammonium salt.

[0139] As the water-soluble quaternary ammonium salt, is preferably useda quaternary alkylammonium salt, and the quaternary alkylammonium saltis preferably a compound represented by the following formula (1):

[NR₄ ⁺[OH]⁻  (1)

[0140] wherein R is an alkyl group having 1 to 4 carbon atoms.

[0141] Incidentally, 4 R groups may be the same or different from oneanother.

[0142] As specific examples thereof, the same compounds as thoseexemplified as the water-soluble quaternary ammonium salt making up thefirst slurry are mentioned by way of example. Among these,tetramethylammonium hydroxide and tetraethylammonium hydroxide areparticularly preferably used.

[0143] Examples of another basic organic compound than the water-solublequaternary ammonium salt include water-soluble amines.

[0144] Examples of the water-soluble amines include (1) alkylamines suchas methylamine, dimethylamine, trimethylamine, ethylamine, diethylamineand triethylamine, (2) alkanolamines such as diethanolamine,triethanolamine and aminoethylethanolamine, (3) alkyleneamines such asdiethylenetriamine, triethylenetetramine, tetraethylenepentamine,pentaethylenehexamine and triethylenediamine, and (4) imines such asethyleneimine. Among these, diethanolamine, triethanolamine and the likeare preferably used.

[0145] A salt of any of the above-mentioned amines may be used as thewater-soluble amine.

[0146] The water-soluble amines may be used either singly or in anycombination thereof.

[0147] The mixing proportions of the water-soluble quaternary ammoniumsalt and another basic organic compound (hereinafter also referred to as“specific basic organic compound”) than the water-soluble quaternaryammonium salt may be both 0.005 to 10% by mass, preferably 0.005 to 8%by mass, more preferably 0.008 to 5% by mass, particularly preferably0.01 to 4% by mass based on the total mass of the second slurry in theform of the all components-containing type slurry or two-liquid mixedtype slurry. If the mixing proportion of the specific basic organiccompound is lower than 0.005% by mass, a sufficient polishing rate maynot be achieved in some cases. It is not necessary to contain thespecific basic organic compound in a proportion exceeding 10% by mass.

[0148] The specific basic organic compound is dissolved in the slurry,and a part thereof is contained as an ion.

[0149] [2] Inorganic Acid Salt:

[0150] As the inorganic acid salt, may be used any of the compoundsexemplified as the compound usable as the inorganic acid salt making upthe first slurry.

[0151] The mixing proportion of the inorganic acid salt may be 0.005 to8% by mass, preferably 0.005 to 6% by mass, more preferably 0.008 to 4%by mass, particularly preferably 0.01 to 3% by mass based on the totalmass of the second slurry in the form of the all components-containingtype slurry or two-liquid mixed type slurry.

[0152] If the mixing proportion of the inorganic acid salt is lower than0.005% by mass, the effect of preventing dishing and erosion may becomeinsufficient in some cases. It is not necessary to contain the inorganicacid salt in a proportion exceeding 8% by mass.

[0153] [3] Water-Soluble Polymer:

[0154] Examples of the water-soluble polymer include cellulosederivatives such as methyl cellulose, methylhydroxyethyl cellulose,methylhydroxypropyl cellulose, hydroxyethyl cellulose, hydroxypropylcellulose, carboxymethyl cellulose, carboxyethyl cellulose, andcarboxymethylhydroxyethyl cellulose; polysaccharides such as chitosan;and besides water-soluble polymers such as polyethylene glycol,polyethyleneimine, polyvinyl pyrrolidone, polyvinyl alcohol, polyacrylicacid and salts thereof, polyacrylamide and polyethylene oxide. Amongthese, cellulose derivatives, and polyacrylic acid and salts thereof arepreferred, with hydroxyethyl cellulose and carboxymethyl cellulose beingmore preferred.

[0155] These water-soluble polymers may be used either singly or in anycombination thereof.

[0156] The mixing proportion of the water-soluble polymer may be 0.001to 5% by mass, preferably 0.001 to 3% by mass, more preferably 0.003 to2% by mass, particularly preferably 0.005 to 1% by mass based on thetotal mass of the second slurry in the form of the allcomponents-containing type slurry or two-liquid mixed type slurry.

[0157] If the mixing proportion of the water-soluble polymer is lowerthan 0.001% by mass, the effect of preventing dishing and erosion maybecome insufficient in some cases, and surface defects may be increased.It is not necessary to contain the water-soluble polymer in a proportionexceeding 5% by mass.

[0158] [4] Abrasive Grains:

[0159] In the second slurry, the abrasive grains are contained as anessential component in the all components-containing type slurry, andcontained in at least one of the first aqueous dispersion material (I)and the second aqueous dispersion material (II) in the two-liquid mixedtype slurry.

[0160] As the abrasive grains, may be used any of the particlesexemplified as the particles usable as the abrasive grains making up thefirst slurry.

[0161] The mixing proportion of the abrasive grains may be controlled to0.01 to 10% by mass, preferably 0.03 to 8% by mass, particularlypreferably 0.05 to 5% by mass based on the total mass of the secondslurry in the form of the all components-containing type slurry ortwo-liquid mixed type slurry. If the mixing proportion of the abrasivegrains is lower than 0.01% by mass, the resulting slurry cannot achieveany sufficient polishing rate. If the mixing proportion exceeds 10% bymass on the other hand, the resulting slurry becomes high cost and maybe deteriorated in shelf stability in some cases.

[0162] [5] Aqueous Medium:

[0163] The all components-containing type slurry or the first aqueousdispersion material (I) and the second aqueous dispersion material (II)in the two-liquid mixed type slurry making up the second slurry arerespectively obtained by mixing the above-described respectivecomponents, and optionally contained components into an aqueous mediumto disperse them in the aqueous medium. As the aqueous medium, may beused water, a mixed medium comprising water and a water-soluble alcoholin an amount or proportion within a range not impairing the polishingperformance, or the like. However, water is particularly preferred.

[0164] [6] Other Components:

[0165] The all components-containing type slurry is obtained by mixingthe water-soluble quaternary ammonium salt, another basic organiccompound than the water-soluble quaternary ammonium salt, the inorganicacid salt, the water-soluble polymer and the abrasive grains into theaqueous medium as described above and may contain additives such asorganic acids or salts thereof, oxidizing agents and/or surfactants asneeded in addition to the above-described components.

[0166] These other additives may also be contained in the two-liquidmixed type slurry. In this case, the other additives may be contained inat least one of the first aqueous dispersion material (I) and the secondaqueous dispersion material (II).

[0167] As the organic acids and the salts thereof, the oxidizing agentsand the surfactants, may be mentioned the same compounds as thoseexemplified as those which can be contained in the first slurry.

[0168] In the two-liquid mixed type slurry, the water-soluble polymermay also be contained in the first aqueous dispersion material (I) asneeded.

[0169] Specific examples of the water-soluble polymer include thepolymers exemplified as those usable as the polymer making up the secondaqueous dispersion material (II).

[0170] When the water-soluble polymer is also contained in the firstaqueous dispersion material (I), the total mixing proportion of thewater-soluble polymer contained in both of the first aqueous dispersionmaterial (I) and the second aqueous dispersion material (II) may be0.001 to 5% by mass, preferably 0.001 to 3% by mass, more preferably0.003 to 2% by mass, particularly preferably 0.005 to 1% by mass basedon the total mass of the two-liquid mixed type slurry.

[0171] The mixing proportion of the water-soluble polymer is controlledwithin the above range, whereby the resulting slurry can achievesufficient polishing characteristics and becomes stable.

[0172] In the case of the all components-containing type slurry, theseadditives, which may be optionally contained as needed, may be mixedupon preparation thereof, or may also be mixed in a supply line of theslurry or on a polishing table upon the practice of the chemicalmechanical polishing step by separately preparing an aqueous solutionthereof.

[0173] In the case of the two-liquid mixed type slurry, these additivesmay be respectively mixed upon preparation of the first aqueousdispersion material (I) and the second aqueous dispersion material (II),may be mixed upon mixing of the first aqueous dispersion material (I)with the second aqueous dispersion material (II), or may also be mixedin a supply line of the slurry or on a polishing table upon the practiceof the chemical mechanical polishing step by separately preparing anaqueous solution thereof.

[0174] The preferable pH of the second slurry is preferably within thesame range as the preferable pH range in the first slurry.

[0175] Examples of a film to be polished with the second slurry includesilicon type films such as silicon oxide films, polysilicon films,monocrystalline silicon films, amorphous silicon films and siliconnitride films, pure metal films such as pure tungsten films, purealuminum films and pure copper films, and alloy films composed of analloy of tungsten, aluminum or copper with any other metal. Stopperlayers (barrier layers) composed of a metal such as tantalum ortitanium, an oxide such as tantalum oxide or titanium oxide, or anitride such as titanium nitride or tantalum nitride may also bementioned. The second slurry may be suitably used in polishing of,particularly, silicon type films among these.

[0176] With respect to the above “polysilicon film” and “amorphoussilicon film”, arsenic, phosphorus or the like may be doped intopolysilicon and amorphous silicon respectively forming these films. Thesame shall apply to the polysilicon films and amorphous silicon filmsdescribed at other places in this specification.

[0177] When chemical mechanical polishing is conducted with the secondslurry, the polishing is conducted with the slurry, in which the mixingproportions of the respective components and the optionally containedcomponents described as above fall within the ranges of the specificmixing proportions. The second slurry used in this polishing may beprepared by mixing the respective components in amounts corresponding tothe specific mixing proportions. Alternatively a high-concentrationproduct of a state that concentrations of the respective components arehigher than the concentrations in a polishing applicable state to beactually served for polishing may be prepared in advance, and thishigh-concentration product may be diluted with water or the like uponthe polishing in such a manner that the mixing proportions of therespective components amount to the specific mixing proportions.

[0178] The high-concentration product of the second slurry is obtainedby mixing the respective components in such a manner that the range of aratio regarding to the mixing proportions of the respective componentsequals to the range of a ratio regarding to the specific mixingproportions, and the mixing proportions of the respective components atthis time are preferably such that the water-soluble quaternary ammoniumsalt is at most 10% by mass, the inorganic acid salt is at most 10% bymass, and the abrasive grains are at most 20% by mass, all based on thetotal mass of the high-concentration product.

[0179] The second slurry can exhibit the initial polishing performancein the case where it is used, by diluting it as required, in a chemicalmechanical polishing step after stored for a long period of time evenwhen the slurry is either a slurry in a polishing applicable stateprepared by mixing the respective components in amounts corresponding tothe specific mixing proportions or a slurry in a high-concentrationstate.

[0180] For example, the second slurry can exhibit the initialperformance even when it is used in the polishing step after it isstored at 40° C. for 30 days or for 90 days in a high-concentrationstate and diluted.

[0181] When the two-liquid mixed type slurry is used to perform thechemical mechanical polishing step, the first aqueous dispersionmaterial (I) and the second aqueous dispersion material (II) may bemixed for use in a line for feeding the slurry, or may be separately fedto a polishing table of a chemical mechanical polishing apparatus andmixed for use on the polishing table. Further, the first aqueousdispersion material (I) and the second aqueous dispersion material (II)may also be mixed in advance to store the resultant mixture in a tank orthe like before use. In this case, the mixture may preferably be usedbefore the stability of the two-liquid mixed type slurry isdeteriorated.

[0182] No particular limitation is imposed on a ratio of the firstaqueous dispersion material (I) to the second aqueous dispersionmaterial (II) so far as intended polishing rate is achieved, dishing,erosion, scratches and the like are sufficiently prevented, andexcellent stability is achieved. However, the ratio [(I)/(II)] of thefirst aqueous dispersion material (I) to the second aqueous dispersionmaterial (II) is preferably 30/70 to 70/30 in terms of a mass ratio.

[0183] [7] Chemical Mechanical Polishing of Surface to be Polished:

[0184] The second chemical mechanical polishing process according to thepresent invention comprises the step of polishing a surface to bepolished with the second slurry.

[0185] When chemical mechanical polishing of the surface to be polishedis carried out with the second slurry, the polishing apparatusexemplified as the polishing apparatus usable in the first chemicalmechanical polishing process using the first slurry can be used toconduct the polishing under the prescribed polishing conditions.

[0186] According to an embodiment of the second chemical mechanicalpolishing process of the present invention, for example, a grooveportion is formed on a semiconductor substrate (also including asemiconductor wafer), a silicon type film such as a polysilicon film oramorphous silicon film is formed on the whole surface of thesemiconductor substrate including this groove, the silicon type film isthen subjected to a polishing treatment using such a chemical mechanicalpolishing apparatus as described above and the second slurry to removeother portions of the silicon type film than a portion buried in thegroove portion, whereby a buried groove having excellent surfacecharacteristics and composed of silicon such as the polysilicon film oramorphous silicon film can be formed in the groove portion formed on thesemiconductor substrate.

[0187] According to another embodiment, a silicon oxide film is formedon a semiconductor substrate (also including a semiconductor wafer), anda groove portion is additionally formed on the resultant stacked film.After silicon such as polysilicon or amorphous silicon is furtherdeposited on the groove portion formed on the stacked film, thedeposited silicon type film is subjected to a polishing treatment usingthe silicon oxide film as a stopper layer, and a surface exposed by thispolishing treatment is treated as a surface to be polished to conduct apolishing treatment using, for example, the above-described chemicalmechanical polishing apparatus and the second slurry, whereby a buriedgroove having excellent surface characteristics and composed of siliconcan be formed in the groove portion formed on the stacked film obtainedby stacking the silicon oxide film on the semiconductor substratebecause the second slurry has excellent polishing and removalselectivity as to the silicon type film and the silicon oxide film. Inthis embodiment, even when a polishing treatment is conducted in thesame manner as in said embodiment except that a nitride film such as atitanium nitride film, tantalum nitride film or silicon nitride film isformed in place of the silicon oxide film, and this nitride film is usedas a stopper layer, a buried groove having excellent surfacecharacteristics and composed of the silicon such as the polysilicon filmor amorphous silicon film can be formed in the groove portion formed onthe stacked film obtained by stacking the nitride film on thesemiconductor substrate because the second slurry has excellentpolishing and removal selectivity as to the silicon type film and thenitride film.

[0188] According to a further embodiment, a monocrystalline silicon filmcan be polished in a specular state using the above-described chemicalmechanical polishing apparatus and the second slurry.

[0189] According to a still further embodiment, a groove portion isformed on a semiconductor substrate, a wiring material film such as apure metal film such as a pure tungsten film, pure aluminum film or purecopper film, or an alloy film composed of an alloy of tungsten, aluminumor copper with any other metal is formed on the whole surface of thesemiconductor substrate including this groove, and a polishing treatmentis then conducted using the above-described chemical mechanicalpolishing apparatus and the second slurry to remove other portions ofthe wiring material film than a portion buried in the groove portion,whereby a buried wiring having excellent surface characteristics can beformed in the groove portion formed on the semiconductor substrate.Incidentally, a stopper layer composed of a metal such as tantalum ortitanium, an oxide such as a tantalum oxide or titanium oxide, a nitridesuch as titanium nitride or tantalum nitride or the like is generallyformed on the surface of the groove formed on the semiconductorsubstrate, the wiring material film is formed on the surface of thestopper layer, and the polishing treatment is then conducted. In thiscase, a buried wiring having excellent surface characteristics can beformed because the second slurry has excellent polishing and removalselectivity as to the wiring material film and the stopper layer.

[0190] The evaluation of the polishing and removal selectivity as to thesilicon type film such as the polysilicon film or amorphous silicon filmand the silicon oxide film, the polishing and removal selectivity as tothe silicon type film and the nitride film and the polishing and removalselectivity as to the wiring material film and the stopper layer can bemade by polishing the respective films to be polished under the sameconditions to compare them, specifically, by determining a ratio ofpolishing rates between the films. The term, “the same conditions” meansthat a polishing apparatus of a specific model is used, and the rotatingspeeds of the platen and head thereof, polishing pressure, polishingtime, the kind of a polishing pad used and a feed rate of the aqueousdispertion for chemical mechanical polishing per unit time are made thesame. The “ratio of polishing rates” can be calculated out from thevalue of the respective polishing rates of (1) the silicon type filmsuch as the polysilicon film or amorphous silicon film, (2) the siliconoxide film or nitride film that becomes a stopper layer, and (3) thewiring material film when these films are separately polished under thesame conditions.

[0191] In the second chemical mechanical polishing process of thepresent invention, a first specific polishing rate ratio represented bya ratio of the polishing rate of a polysilicon film to the polishingrate of a silicon oxide film in the case where the silicon oxide filmand polysilicon film are polished under the same conditions may becontrolled to at least 30, preferably at least 100, particularlypreferably at least 300. Alternatively, a second specific polishing rateratio represented by a ratio of the polishing rate of a polysilicon filmto the polishing rate of a nitride film in the case where the nitridefilm and polysilicon film are polished under the same conditions may becontrolled to at least 50, preferably at least 100, particularlypreferably at least 300.

[0192] After completion of the polishing treatment, the abrasive grainsremaining on the polished surface are preferably removed. The removal ofthe abrasive grains can be conducted by the removing method exemplifiedas the removing method usable after completion of the chemicalmechanical polishing using the first slurry.

[0193] [8] Production Process of Semiconductor Device:

[0194] The second production process of a semiconductor device accordingto the present invention is a process for producing a semiconductordevice using the above mentioned second slurry.

EXAMPLES Examples Related to First Slurry

[0195] [1] Preparation of Aqueous Dispersion Containing Abrasive GrainsComposed of Inorganic Particles or Composite Particles:

[0196] (1) Preparation of Aqueous Dispersion Containing InorganicParticles:

[0197] (a) Preparation of Aqueous Dispersion Containing Fumed SilicaParticles:

[0198] Fumed silica particles (product of Nippon Aerosil Co., Ltd.;trade name “Aerosil #50”) in an amount of 2 kg were added into 6.7 kg ofion-exchanged water and dispersed by means of an ultrasonic dispersingmachine, and the dispersion was then filtered through a filter having apore size of 5 μm to prepare an aqueous dispersion containing the fumedsilica particles. The average primary particle diameter of the silicaparticles in this aqueous dispersion was 30 nm, and the averagesecondary particle diameter thereof was 230 nm.

[0199] (b) Preparation of Aqueous Dispersion Containing ColloidalSilica:

[0200] A 2-liter flask was charged with 70 g of aqueous ammonia(concentration: 25% by mass), 40 g of ion-exchanged water, 175 g ofethanol and 21 g of tetraethoxysilane, and the mixture was heated to 60°C. with stirring at 180 rpm. After the mixture was continuously stirredfor 2 hours at this temperature, it was cooled to obtain an ethanoldispersion of colloidal silica. A process of removing ethanol by meansof an evaporator while adding ion-exchanged water at 80° C. was repeatedseveral times to prepare an aqueous dispersion containing 20% by mass ofcolloidal silica having an average primary particle diameter of 35 nmand an average secondary particle diameter of 70 nm.

[0201] Each of an aqueous dispersion containing 20% by mass of colloidalsilica having an average primary particle diameter of 15 nm and anaverage secondary particle diameter of 25 nm, and an aqueous dispersioncontaining 20% by mass of colloidal silica having an average primaryparticle diameter of 70 nm and an average secondary particle diameter of150 nm were also prepared in substantially the same manner as describedabove except that the amounts of ethanol and tetraethoxysilane addedwere changed.

[0202] (2) Preparation of Aqueous Dispersion Containing Abrasive GrainsComposed of Composite Particles:

[0203] (a) Preparation of Aqueous Dispersion Containing PolymerParticles:

[0204] A 2-liter flask was charged with 90 parts by mass (hereinafterreferred to as “parts” merely) of methyl methacrylate, 5 parts ofmethoxypolyethylene glycol methacrylate (product of Shin-NakamuraChemical Co., Ltd.; trade name “NK Ester M-90G, #400”), 5 parts of4-vinylpyridine, 2 parts of an azo type polymerization initiator(product of Wako Pure Chemical Industries, Ltd.; trade name “V50”) and400 parts of ion-exchanged water, and the mixture was heated to 70° C.with stirring under a nitrogen gas atmosphere to conduct polymerizationfor 6 hours at the same temperature, thereby obtaining an aqueousdispersion containing polymer particles having an average particlediameter of 150 nm, where the said polymer having an amino group and apolyethylene glycol chain. The yield of the polymerization was 95%.

[0205] (b) Preparation of Aqueous Dispersion Containing CompositeParticles:

[0206] One hundred parts of the aqueous dispersion containing 10% bymass of the polymer particles obtained in the above step (a) were addedto a 2-liter flask, 1 part of methyltrimethoxysilane was additionallyadded, and the resultant mixture was stirred at 40° C. for 2 hours.Thereafter, the pH of the mixture was adjusted to 2 with nitric acid toobtain Aqueous Dispersion (1-a). The pH of an aqueous dispersioncontaining 10% by mass of colloidal silica (product of Nissan ChemicalIndustries, Ltd.; trade name “Snowtex O”, average primary particlediameter: 10 to 20 nm) was adjusted to 8 with potassium hydroxide toobtain Aqueous Dispersion (1-b). Incidentally, the zeta potential of thepolymethyl methacrylate particles contained in Aqueous Dispersion (1-a)was +17 mV, while the zeta potential of the silica particles containedin Aqueous Dispersion (1-b) was −40 mV.

[0207] After 50 parts of Aqueous Dispersion (1-b) were gradually addedto and mixed with 100 parts of Aqueous Dispersion (1-a) over 2 hours,the resultant mixture was additionally stirred for 2 hours to obtain anaqueous dispersion containing particles with the colloidal silicaparticles bonded to the polymer particles. To this aqueous dispersion,were added 2 parts of vinyltriethoxysilane, and the mixture was stirredfor 1 hour. Thereafter, 1 part of tetraethoxysilane was added, and themixture was heated to 60° C., continuously stirred for 3 hours at thattemperature and then cooled, thereby obtaining an aqueous dispersioncontaining composite particles. The average particle diameter of thecomposite particles was 180 nm. Composite Particles were such that thesilica particles adhered to the surfaces of the polymer particles so asto cover 80% thereof.

[0208] [2] Preparation of High-Concentration Product of AqueousDispersion for Chemical Mechanical Polishing:

[0209] An ion-exchanged water in an amount that the total mass of theresulting high-concentration product amounted to 100% by mass was addedto a 1-liter polyethylene bottle, an aqueous solution oftetramethylammonium hydroxide the concentration of which was 25% by masswas added to the ion-exchanged water so as to give a concentration of 6%by mass in terms of the tetramethylammonium hydroxide content, and themixture was fully stirred. Thereafter, an aqueous solution(concentration: 20% by mass) of ammonium carbonate was added withstirring so as to give a concentration of 5.5% by mass in terms of theammonium carbonate content, and at the same time 9% by mass of colloidalsilica (average primary particle diameter: 35 nm; average secondaryparticle diameter: 70 nm) was added. After the resultant mixture wasfully stirred, it was filtered through a filter having a pore size of 5μm to obtain High-Concentration Product [1Ad] of Slurry [1A].

[0210] Respective High-Concentration Products [1Bd] to [1Id] of Slurries[1B] to [1I] were obtained in substantially the same manner as describedabove except that the kinds and mixing amounts of the respectivecomponents were changed as shown in Table 1.

[0211] An ion-exchanged water in an amount that the total mass of theresulting high-concentration product amounted to 100% by mass was addedto a 1-liter polyethylene bottle, and the aqueous solutions shown in therow of “Additive 1” of Table 2 were respectively added to theion-exchanged water so as to give the respective mixing amounts shown inthe row of “Additive 1” of Table 2, and the resultant mixtures werefully stirred. Thereafter, the aqueous solutions shown in the row of“Additive 2” of Table 2 were respectively added with stirring so as togive the respective mixing amounts shown in the row of “Additive 2” ofTable 2. At the same time, abrasive grains were added, the resultantmixtures were fully stirred, and they were respectively filtered througha filter having a pore size of 5 μm to obtain High-ConcentrationProducts [1ad] to [1ed] of Comparative Slurries [1a] to [1e].

[0212] The particle diameters of the abrasive grains shown in Tables 1and 2 were described in order of average primary particle diameter andaverage secondary particle diameter as to the colloidal silica, and onlythe average secondary particle diameter was described as to the fumedsilica. As the particle diameter of the composite particles, wasdescribed an average particle diameter.

[0213] Abbreviations in Tables 1 and 2 mean the following compounds,respectively.

[0214] TMAH: tetramethylammonium hydroxide (25% by mass aqueoussolution);

[0215] TEAH: tetraethylammonium hydroxide (20% by mass aqueoussolution);

[0216] TPAH: tetrapropylammonium hydroxide (15% by mass aqueoussolution).

[0217] Ammonium nitrate mentioned in Table 1 was used in the form of a20% by mass aqueous solution, KOH mentioned in Table 2 was used in theform of a 10% by mass aqueous solution, diethanolamine was used in theform of a 10% by mass aqueous solution, HCl was used at a concentrationof 30% by mass, and these were respectively described as “Ammoniumnitrate”, “KOH”, “Diethanolamine” and “HCl” and mixed so as to give therespective mixing amounts shown in the tables. TABLE 1 High- Concen-tration Quaternary Alkyl Inorganic Acid Salt Abrasive Grain ProductAmmonium Salt Amount Particle Other Additives of Amount Mixed DiameterAmount Amount Slurry Kind Mixed (wt %) Kind (wt %) Kind (nm) Mixed (wt%) Kind Mixed (wt %) 1Ad TMAH 6 Ammonium 5.5 Colloidal 35, 70 9 None —Carbonate Silica 1Bd TMAH 3 Ammonium 1.6 Colloidal 15, 25 9 None —Carbonate Silica 1Cd TEAH 3 Ammonium 1.6 Colloidal 35, 70 9 None —Nitrate Silica 1Dd TMAH 2 Ammonium 0.9 Colloidal 35, 70 9 Ammonia 1Nitrate Silica 1Ed TMAH 3 Ammonium 1.4 Fumed 230 6 None — CarbonateSilica 1Fd TPAH 0.6 Ammonium 0.6 Colloidal 70, 150 1.8 None — CarbonateSilica 1Gd TEAH 4.5 Ammonium 4 Colloidal 35, 70 4.5 None — CarbonateSilica 1Hd TMAH 3 Ammonium 1.6 Composite 180 5 None — Carbonate Particle1Id TMAH 6 Ammonium 5.5 Colloidal 35, 70 9 Hydroxyethyl 0.05 NitrateSilica Cellulose

[0218] TABLE 2 High- Abrasive Grain Concentration Additive 1 Additive 2Particle Product of Amount Amount Diameter Amount Slurry Kind Mixed (wt%) Kind Mixed (wt %) Kind (nm) Mixed (wt %) 1ad TMAH 4 HCl 3 Colloidal35, 70 6 Silica 1bd TMAH 6 None — Colloidal 15, 25 6 Silica 1cdDiethanolamine 5 None — Fumed 230 6 Silica 1dd KOH 5 None — Colloidal70, 150 9 Silica 1ed KOH 5 HCl 3 Colloidal 70, 150 9 Silica

[0219] [3] Preparation of Aqueous Dispersion for Chemical MechanicalPolishing:

[0220] After High-Concentration Products [1Ad] to [1Id] and [1ad] to[1ed] prepared in the step [2] were left to stand at 25° C. for 2 hoursafter the preparation, parts thereof were taken out, and ion-exchangedwater was added thereto to dilute them to the respective dilution ratesshown in Tables 3 and 4 to obtain Slurries [1A] to [1I] and ComparativeSlurries [1a] to [1e] The contents of the respective components and pHvalues of each of the slurries thus obtained are shown in Tables 3 and4.

[0221] After the high-concentration products were stored at 40° C. for90 days, they were diluted in the same manner as described above toobtain Slurries [1A] to [1I] and Comparative Slurries [1a] to [1e]. ThepH values of the each of the slurries thus obtained are shown in Tables3 and 4.

[0222] Abbreviations, TMAH, TEAH and TPAH in Tables 3 and 4 mean thesame compounds as in Tables 1 and 2. TABLE 3 Quaternary Alkyl pHAmmonium Salt Inorganic Acid Salt Abrasive Grain Other Additives DilutedDiluted Amount Amount Particle Amount Amount 2 Hours 90 Days DilutionMixed Mixed Diameter Mixed Mixed After After Slurry Rate Kind (wt %)Kind (wt %) Kind (nm) (wt %) Kind (wt %) Preparation Preparation 1A 10TMAH 0.6 Ammonium 0.55 Colloidal 35, 70 0.9 None — 10.5 10.3 CarbonateSilica 1B 10 TMAH 0.3 Ammonium 0.16 Colloidal 15, 25 0.9 None — 10.610.4 Carbonate Silica 1C 10 TEAH 0.3 Ammonium 0.16 Colloidal 35, 70 0.9None — 10.6 10.5 Nitrate Silica 1D 10 TMAH 0.2 Ammonium 0.09 Colloidal35, 70 0.9 Ammonia 0.1  11.0 11.1 Carbonate Silica 1E 10 TMAH 0.3Ammonium 0.14 Fumed 230 0.6 None — 11.0 11.0 Carbonate Silica 1F 2 TPAH0.3 Ammonium 0.3 Colloidal 70, 150 0.9 None — 9.2 9.1 Carbonate Silica1G 5 TEAH 0.9 Ammonium 0.8 Colloidal 35, 70 0.9 None — 10.6 10.4Carbonate Silica 1H 10 TMAH 0.3 Ammonium 0.16 Composite 180 0.5 None —10.6 10.5 Carbonate Particle 1I 10 TMAH 0.6 Ammonium 0.55 Colloidal 35,70 0.9 Hydroxy- 0.005 10.5 10.3 Nitrate Silica ethyl Cellulose

[0223] TABLE 4 pH Abrasive Grain Diluted Diluted Additive 1 Additive 2Particle 2 hours 90 days Dilution Amount Amount Diameter Amount AfterAfter Slurry Rate Kind Mixed (wt %) Kind Mixed (wt %) Kind (nm) Mixed(wt %) Preparation Preparation 1a 10 TMAH 0.4 HCl 0.3 Colloidal 35, 700.6 10.3 10.1 silica 1b 10 TMAH 0.6 None — Colloidal 15, 25 0.6 12.111.5 Silica 1c 10 Diethanolamine 0.5 None — Fumed 230 0.6 11.2 11.3Silica 1d 10 KOH 0.5 None — Colloidal 70, 150 0.9 12.2 11.5 Silica 1e 10KOH 0.5 HCl 0.3 Colloidal 70, 150 0.9 10.5 10.5 Silica

[0224] [4] Evaluation of Polishing Performance on Polysilicon Film:

Example 1-1

[0225] (i) Evaluation of Polishing Rate Upon Polishing of PolysiliconFilm:

[0226] Slurry [1A] (product diluted after 2 hours form the preparation)prepared in the step [3] was used, and an 8-inch silicon substratehaving a thermal oxidation film was placed on a chemical mechanicalpolishing apparatus (Model “EPO112”, manufactured by Ebara Corporation)to polish a polysilicon film (film thickness: 5,000 Å) formed on thesubstrate by means of a polishing pad (product of Rodel Nitta, Ltd.;trade name “IC1000”) made of porous polyurethane under the followingconditions. The polishing rate of the polysilicon film was found to be4250 Å/min.

[0227] Carrier load: 300 g/cm²

[0228] Carrier rotating speed: 50 rpm

[0229] Platen rotating speed: 55 rpm

[0230] Feed rate of slurry: 200 ml/min

[0231] Polishing time: 1 minute

[0232] [ii] Evaluation of Polishing and Removal Selectivity as toPolysilicon Film and Silicon Oxide Film:

[0233] The polishing rate of a silicon oxide film was determined in thesame manner as in the evaluation [i] except that an 8-inch silicon oxidefilm substrate (film thickness: 5,000 Å) was used in place of the 8-inchsilicon substrate having a thermal oxidation film in the evaluation [i].As a result, the polishing rate of silicon oxide film was 5 Å/min. Fromthis fact, the polishing and removal selectivity as to the polysiliconfilm and the silicon oxide film of Slurry [1A] was able to be calculatedas 850.

[0234] [iii] Evaluation of Polishing and Removal Selectivity as toPolysilicon Film and Silicon Nitride Film:

[0235] The polishing rate of a silicon nitride film was determined inthe same manner as in the evaluation [i] except that an 8-inch siliconnitride film substrate (film thickness: 1,000 Å) was used in place ofthe 8-inch silicon substrate having a thermal oxidation film in theevaluation [i]. As a result, the polishing rate was 5 Å/min. From thisfact, the polishing and removal selectivity as to the polysilicon filmand the silicon nitride film of Slurry [1A] was able to be calculated as850.

[0236] [iv] Evaluation of Erosion:

[0237] A polishing treatment was conducted in the same manner as in theevaluation [i] except that a wafer with polysilicon deposited (amount ofpolisilicon deposited: 3500 Å) on a silicon oxide film including apattern of a wiring 50 μm wide/a non-wiring portion 9 μm wide and apattern of a wiring 2 μm wide/a non-wiring portion 0.35 μm wide was usedin place of the 8-inch silicon substrate having a thermal oxidation filmin the evaluation [i], and the polishing time was set so as to exceed by30% as much as the standard time. After the polishing, erosion at analternate wiring site having the wiring width of 50 μm and an alternatewiring site having the wiring width of 2 μm was measured by means of astep height and surface roughness meter (Model “P-10”, manufactured byKLA-Tencor Co.). As a result, erosion at the alternate wiring sites were750 Å and 600 Å, respectively. When these values are not greater than1000 Å and 700 Å, respectively, the erosion resistance may safely besaid to be good.

[0238] Incidentally, the polishing time exceeding by 30% as much as thestandard time was calculated in the following manner based on thepolishing rate of the polysilicon film measured in the evaluation [i]and performed.

Polishing time (min)=[Amount of polysilicon deposited (Å)/Polishing rate(Å/min) of polysilicon film]×1.3

[0239] (v) Evaluation of Stability of High-Concentration product ofSlurry:

[0240] Evaluation as to the respective items was made in substantiallythe same manner as in the evaluation (i) to (iv) except that Slurry [1A]obtained by diluting High-Concentration Product [1Ad] after stored at40° C. for 90 days after the preparation of High-Concentration Product[1Ad] was used in place of Slurry [1A] obtained by dilutingHigh-Concentration Product [1Ad] after 2 hours from the preparation inthe evaluation (i) to (iv). The results are shown in Table 5.

[0241] As apparent from Table 5, it was understood that the performanceof Slurry [1A] is almost the same between the case where ConcentrationProduct [1Ad] was diluted to be used after 2 hours from the preparationand the case where Concentration Product [1Ad] was diluted to be usedafter stored at 40° C. for 90 days after the preparation, and thus hasexcellent long-term stability in a high-concentration state.

Examples 1-2 to 1-7 and Comparative Examples 1-1 to 1-5

[0242] Evaluation was made in substantially the same manner as inExample 1-1 except that their corresponding slurries shown in Tables 5and 6 were used in place of Slurry [1A] in Example 1-1. The results areshown in Tables 5 and 6. TABLE 5 Example 1-1 Example 1-2 Example 1-3Example 1-4 Example 1-5 Example 1-6 Example 1-7 Slurry 1A 1C 1D 1F 1G 1H1I Diluted Polishing Rate of 4250 2600 3100 1800 4450 2500 2000 2 hoursPolysilicon after Film (Å/min) Preparation Ratio of Polishing rate 850430 365 300 890 500 285 Polysilicon: Silicon Oxide Ratio of Polishingrate 850 520 475 360 740 625 285 Polysilicon: Silicon Nitride Erosion(Å) 750 600 650 850 900 700 450 Wiring Width 50 μm Wiring Width 2 μm 600550 500 700 700 500 400 Diluted Polishing Rate of 4100 2650 3150 16504400 2600 2100 90 days Polysilicon after Film (Å/min) Preparation Ratioof Polishing rate 820 405 395 330 735 520 300 Polysilicon: Silicon OxideRatio of Polishing rate 970 530 450 365 735 650 280 Polysilicon: SiliconNitride Erosion (Å) 800 650 750 900 950 750 450 Wiring Width 50 μmWiring Width 2 μm 550 550 450 650 650 550 400

[0243] TABLE 6 Comparative Comparative Comparative ComparativeComparative Example 1-1 Example 1-2 Example 1-3 Example 1-4 Example 1-5Slurry 1a 1b 1c 1d 1e Diluted Polishing Rate of 1300 2850 200 2300 11002 days Polysilicon after Film (Å/min) Preparation Ratio of Polishingrate 15 30 less than 1 10 10 Polysilicon: Silicon Oxide Ratio ofPolishing rate 90 15 60 20 100 Polysilicon: Silicon Nitride Erosion (Å)1050 1450 500 1200 950 Wiring Width 50 μm Wiring Width 2 μm 900 1800 4001300 950 Diluted Polishing Rate of 1100 1200 200 1550 200 90 daysPolysilicon after Film (Å/min) Preparation Ratio of Polishing rate 10 5less than 1 5 less than 1 Polysilicon: Silicon Oxide Ratio of Polishingrate 80 5 50 15 30 Polysilicon: Silicon Nitride Erosion (Å) 1000 2050550 1650 1000 Wiring Width 50 μm Wiring Width 2 μm 950 2250 400 1700 900

[0244] [5] Evaluation of Polishing Performance on MonocrystallineSilicon Film:

Example 1-8

[0245] (vi) Evaluation of Polishing Rate of Monocrystalline SiliconFilm:

[0246] Slurry [1B] (product diluted after 2 hours form the preparation)prepared in the step [3] was used, and a silicon wafer (product of E & MCo.) was placed on a chemical mechanical polishing apparatus (Model“EPO112”, manufactured by Ebara Corporation) to conduct polishing bymeans of a polishing pad (product of Rodel Nitta, Ltd.; trade name“IC1000”) made of porous polyurethane under the following conditions.The polishing rate of the monocrystalline silicon film was found to be1800 Å/min.

[0247] Carrier load: 300 g/cm²

[0248] Carrier rotating speed: 50 rpm

[0249] Platen rotating speed: 55 rpm

[0250] Feed rate of slurry: 200 ml/min

[0251] Polishing time: 3 minutes

[0252] (vii) Evaluation of Stability of High-Concentration Product ofSlurry:

[0253] Evaluation was carried out in substantially the same manner as inthe evaluation (vi) except that Slurry [1B] obtained by dilutingHigh-Concentration Product [1Bd] after stored at 40° C. for 90 daysafter the preparation was used in place of Slurry [1B] obtained bydiluting High-Concentration Product [1Bd] after 2 hours from thepreparation in the evaluation (vi).

[0254] As a result, the polishing rate of the monocrystalline siliconfilm was 1750 Å/min, and there was little difference from the case whereHigh-Concentration Product [1Bd] was diluted after 2 hours from thepreparation.

Example 1-9

[0255] Evaluation was carried out in substantially the same manner as inExample 1-8 except that Slurry [1E] was used in place of Slurry [1B] inExample 1-8.

[0256] As a result, with respect to Slurry [1E] diluted after 2 hoursfrom the preparation, the polishing rate of the monocrystalline siliconfilm was 2200 Å/min, while with respect to Slurry [1E] diluted afterstored at 40° C. for 90 days after the preparation of High-ConcentrationProduct [1Ed], the polishing rate of the monocrystalline silicon filmwas 2320 Å/min and was not lowered at all compared with the case whereHigh-Concentration Product [1Ed] was diluted after 2 hours from thepreparation.

Examples Related to Second Slurry

[0257] [1] Preparation of Aqueous Dispersion Containing Abrasive GrainsComposed of Inorganic Particles or Composite Particles:

[0258] (1) Preparation of Aqueous Dispersion Containing InorganicAbrasive Grains (Colloidal Silica):

[0259] A 2-liter flask was charged with 70 g of aqueous ammonia(concentration: 25% by mass), 40 g of ion-exchanged water, 175 g ofethanol and 21 g of tetraethoxysilane, and the mixture was heated to 60°C. with stirring at 180 rpm. After the mixture was continuously stirredfor 2 hours at this temperature, it was cooled to obtain an ethanoldispersion of colloidal silica. A process of removing ethanol by meansof an evaporator while adding ion-exchanged water at 80° C. was repeatedseveral times to prepare an aqueous dispersion containing 20% by mass ofcolloidal silica having an average primary particle diameter of 35 nmand an average secondary particle diameter of 70 nm.

[0260] An aqueous dispersion containing 20% by mass of colloidal silicahaving an average primary particle diameter of 15 nm and an averagesecondary particle diameter of 25 nm was also prepared in substantiallythe same manner as described above except that the amounts of ethanoland tetraethoxysilane added were changed.

[0261] (2) Preparation of Aqueous Dispersion Containing Abrasive GrainsComposed of Composite Particles:

[0262] (a) Preparation of Aqueous Dispersion Containing PolymerParticles:

[0263] A 2-liter flask was charged with 90 parts of methyl methacrylate,5 parts of methoxypolyethylene glycol methacrylate (product ofShin-Nakamura Chemical Co., Ltd.; trade name “NK Ester M-90G, #400”), 5parts of 4-vinylpyridine, 2 parts of an azo type polymerizationinitiator (product of Wako Pure Chemical Industries, Ltd.; trade name“V50”) and 400 parts of ion-exchanged water, and the mixture was heatedto 70° C. with stirring under a nitrogen gas atmosphere to conductpolymerization for 6 hours at the same temperature, thereby obtaining anaqueous dispersion containing polymer particles having an averageparticle diameter of 150 nm, where the said polymer having an aminogroup and a polyethylene glycol chain. The yield of the polymerizationwas 95%.

[0264] (b) Preparation of Aqueous Dispersion Containing CompositeParticles:

[0265] One hundred parts of the aqueous dispersion containing 10% bymass of the polymer particles obtained in the step (a) were added to a2-liter flask, 1 part of methyltrimethoxysilane was additionally added,and the resultant mixture was stirred at 40° C. for 2 hours. Thereafter,the pH of the mixture was adjusted to 2 with nitric acid to obtainAqueous Dispersion (2-a). The pH of an aqueous dispersion containing 10%by mass of colloidal silica (product of Nissan Chemical Industries,Ltd.; trade name “Snowtex O”, average primary particle diameter: 10 to20 nm) was adjusted to 8 with potassium hydroxide to obtain AqueousDispersion (2-b). Incidentally, the zeta potential of the polymethylmethacrylate particles contained in Aqueous Dispersion (2-a) was +17 mV,while the zeta potential of the silica particles contained in AqueousDispersion (2-b) was −40 mV.

[0266] After 50 parts of Aqueous Dispersion (2-b) were gradually addedto and mixed with 100 parts of Aqueous Dispersion (2-a) over 2 hours,the resultant mixture was additionally stirred for 2 hours to obtain anaqueous dispersion containing particles with the colloidal silicaparticles bonded to the polymer particles. To this aqueous dispersion,were added 2 parts of vinyltriethoxysilane, and the mixture was stirredfor 1 hour. Thereafter, 1 part of tetraethoxysilane was added, and themixture was heated to 60° C., continuously stirred for 3 hours at thattemperature and then cooled, thereby obtaining an aqueous dispersioncontaining composite particles. The average particle diameter of thecomposite particles was 180 nm. Composite Particles were such that thesilica particles adhered to the surfaces of the polymer particles so asto cover 80% thereof.

[0267] [2] Preparation of High-Concentration Product of AqueousDispersion for Chemical Mechanical Polishing:

[0268] (a) Preparation of First Aqueous Dispersion Material (I):

[0269] An ion-exchanged water in an amount that the total mass of theresulting high-concentration product amounted to 100% by mass was addedto a 1-liter polyethylene bottle, an aqueous solution oftetramethylammonium hydroxide the concentration of which was 25% by masswas added to the ion-exchanged water so as to give a concentration of 5%by mass in terms of the tetramethylammonium hydroxide content, and themixture was fully stirred. Thereafter, an aqueous solution of ammoniumcarbonate was added with stirring so as to give a concentration of 3% bymass in terms of the ammonium carbonate content, and at the same time 9%by mass of colloidal silica (average primary particle diameter: 35 nm;average secondary particle diameter: 70 nm) was added. After theresultant mixture was fully stirred, it was filtered through a filterhaving a pore size of 5 μm to obtain High-Concentration Product [2Ad] ofAqueous Dispersion [2A] that is First Aqueous Dispersion Material (I)making up a two-liquid mixed type slurry.

[0270] Respective High-Concentration Products [2Bd] to [2Ed] of AqueousDispersions [2B] to [2E] that are First Aqueous Dispersion Materials (I)were obtained in substantially the same manner as described above exceptthat the kinds and mixing amounts of the respective components werechanged as shown in Table 7.

[0271] An ion-exchanged water in an amount that the total mass of theresulting high-concentration product amounted to 100% by mass was addedto a 1-liter polyethylene bottle, and the aqueous solutions shown in therow of “Additive 1” of Table 8 were respectively added to theion-exchanged water so as to give the respective mixing amounts shown inthe row of “Additive 1” of Table 8, and the resultant mixtures werefully stirred. Thereafter, the aqueous solutions shown in the row of“Additive 2” of Table 8 were respectively added with stirring so as togive the respective mixing amounts shown in the row of “Additive 2” ofTable 8. At the same time, abrasive grains were added, the resultantmixtures were fully stirred, and they were respectively filtered througha filter having a pore size of 5 μm to obtain respectiveHigh-Concentration Products [2Fd] and [2Gd] of Aqueous Dispersions [2F]and [2G] that are Comparative First Aqueous Dispersion Materials (I).

[0272] (b) Preparation of Second Aqueous Dispersion Material (II):

[0273] An ion-exchanged water in an amount that the total mass of theresulting high-concentration product amounted to 100% by mass was addedto a 1-liter polyethylene bottle, an aqueous solution of hydroxyethylcellulose was added to the ion-exchanged water so as to give aconcentration of 0.15% by mass in terms of the hydroxyethyl cellulosecontent, and the mixture was fully stirred. Thereafter, an aqueoussolution of triethanolamine and an aqueous solution oftetramethylammonium hydroxide were added with stirring so as to giveconcentrations of 3% by mass and 0.1% by mass in terms of thetriethanolamine content and tetramethylammonium hydroxide content,respectively, and colloidal silica (average primary particle diameter:35 nm; average secondary particle diameter: 70 nm) was added so as togive a mixing amount of 2.5% by mass. After the resultant mixture wasfully stirred, it was filtered through a filter having a pore size of 5μm to obtain High-Concentration Product [2ad] of Aqueous Dispersion [2a]that is Second Aqueous Dispersion Material (II) making up the two-liquidmixed type slurry.

[0274] Respective High-Concentration Products [2bd] to [2dd] of AqueousDispersions [2b] to [2d] that are Second Aqueous Dispersion Materials(II) were obtained in substantially the same manner as described aboveexcept that the kinds and mixing amounts of the respective componentswere changed as shown in Table 7.

[0275] Hydroxyethyl cellulose, and carboxymethyl cellulose used inAqueous Dispersion [2dd] were purified by respectively feeding aqueoussolutions thereof to a resin column packed with a mixture of an H typeion-exchange resin and an OH type ion-exchange resin at a fixed ratefrom one direction to bring them into contact with the ion-exchangeresins.

[0276] An ion-exchanged water in an amount that the total mass of theresulting high-concentration product amounted to 100% by mass was addedto a 1-liter polyethylene bottle, and the aqueous solutions shown in therow of “Additive 3” of Table 8 were respectively added to theion-exchanged water so as to give the respective mixing amounts shown inthe row of “Additive 3” of Table 8, and the resultant mixtures werefully stirred. Thereafter, the aqueous solutions shown in the row of“Additive 4” of Table 8 were respectively added with stirring so as togive the respective mixing amounts shown in the row of “Additive 4” ofTable 8. At the same time, abrasive grains were added, the resultantmixtures were fully stirred, and they were respectively filtered througha filter having a pore size of 5 μm to obtain respectiveHigh-Concentration Products [2ed] and [2fd] of Aqueous Dispersions [2e]and [2f] that are Comparative Second Aqueous Dispersion Materials (II).Incidentally, the particle diameters of the abrasive grains shown inTables 7 and 8 were described in order of average primary particlediameter and average secondary particle diameter as to the colloidalsilica. As the particle diameter of the composite particles, wasdescribed an average particle diameter.

[0277] Abbreviations in Tables 7 and 8 mean the following compounds,respectively.

[0278] TMAH: tetramethylammonium hydroxide (25% by mass aqueoussolution);

[0279] TEAH: tetraethylammonium hydroxide (20% by mass aqueoussolution);

[0280] HEC: hydroxyethyl cellulose (1% by mass aqueous solution);

[0281] CMC: carboxymethyl cellulose (1% by mass aqueous solution).

[0282] Ammonium carbonate in Table 7 was used in the form of a 20% bymass aqueous solution, ammonium nitrate was used in the form of a 20% bymass aqueous solution, and triethanolamine and diethanolamine were usedin the form of a 20% by mass aqueous solution, while KOH in Table 8 wasused in the form of a 10% by mass aqueous solution, and HCl was used ata concentration of 30% by mass. These were respectively prepared so asto give respective mixing amounts shown in Tables 7 and 8. TABLE 7 High-Concentration Quaternary Alkyl Inorganic Acid Salt Abrasive Grain OtherAdditives Product of Ammonium Salt Amount Particle Amount Amount AqueousAmount Mixed Diameter Mixed Mixed Liquid I Dispersion Kind Mixed (wt %)Kind (wt %) Kind (nm) (wt %) Kind (wt %) 2Ad TMAH 5.0 Ammonium Carbonate3.0 Colloidal Silica 35, 70 9.0 None — 2Bd TMAH 3.0 Ammonium Nitrate 1.6Colloidal Silica 15, 25 9.0 None — 2Cd TEAH 4.5 Ammonium Carbonate 4.0Colloidal Silica 35, 70 4.5 None — 2Dd TMAH 3.0 Ammonium Carbonate 1.6Composite 180 5.0 None — Particle 2Ed TMAH 2.0 Ammonium Carbonate 0.9Colloidal Silica 35, 70 9.0 Ammonia 1.0 High- Concentration BasicOrganic Compound Abrasive Grain Other Additives Product of Water SolublePolymer Amount Particle Amount Amount Aqueous Amount Mixed DiameterMixed Mixed Liquid II Dispersion Kind Mixed (wt %) Kind (wt %) Kind (nm)(wt %) Kind (wt %) 2ad HEC 0.15 Triethanolamine 3.0 Colloidal Silica 35,70 2.5 TMAH 0.1  2bd HEC 0.50 Diethanolamine 5.0 Colloidal Silica 15, 256.0 None — 2cd HEC 0.60 Triethanolamine 7.0 Composite 180 6.0 TMAH 0.05Particle 2dd CMC 0.75 Triethanolamine 4.5 None — — None —

[0283] TABLE 8 High- Concentration Abrasive Grain Product of Additive 1Additive 2 Particle Aqueous Amount Amount Diameter Amount Liquid IDispersion Kind Mixed (wt %) Kind Mixed (wt %) Kind (nm) Mixed (wt %)2Fd TMAH 4.0 HCl 3.0 Colloidal 35, 70 6.0 Silica 2Gd KOH 5.0 None —Colloidal 35, 70 9.0 Silica High- Concentration Abrasive Grain Productof Additive 3 Additive 4 Particle Aqueous Amount Amount Diameter AmountLiquid II Dispersion Kind Mixed (wt %) Kind Mixed (wt %) Kind (nm) Mixed(wt %) 2ed HEC 0.5 KOH 0.2 Colloidal 35, 70 2.5 Silica 2fd None —Triethanolamine 5.0 Colloidal 15, 25 6.0 Silica

[0284] Incidentally, in Tables 7 and 8, “Liquid I” and “Liquid II” meanFirst Aqueous Dispersion Material (I) and Second Aqueous DispersionMaterial (II), respectively.

[0285] [3] Preparation of Aqueous Dispersion (Two-Liquid Mixed TypeSlurry) for Chemical Mechanical Polishing:

[0286] After High-Concentration Products [2Ad] to [1Gd] and [2ad] to[2fd] prepared in the above step [2] were left to stand at 25° C. for 2hours after the preparation, parts thereof were taken out, andion-exchanged water was added thereto to dilute them to the respectivedilution rates shown in Tables 9 and 10 to obtain Slurries [2A] to [2G]and Comparative Slurries [2a] to [2f]. The contents of the respectivecomponents and pH values of the slurries thus obtained are shown inTables 9 and 10.

[0287] After the respective high-concentration products of above werestored at 40° C. for 90 days, they were diluted in the same manner asdescribed above to obtain Slurries [2A] to [2G] and Comparative Slurries[2a] to [2f]. The pH values of the slurries thus obtained are shown inTables 9 and 10.

[0288] Abbreviations, TMAH, TEAH, HEC and CMC in Tables 9 and 10 meanthe same compounds as in Tables 7 and 8. TABLE 9 pH Quaternary AlkylDiluted Diluted Ammonium Salt Inorganic Acid Salt Abrasive Grain OtherAdditives 2 hours 90 days Amount Amount Particle Amount Amount afterafter Dilution Mixed Mixed Diameter Mixed Mixed Prepar- Prepar- Liquid ISlurry Rate Kind (wt %) Kind (wt %) Kind (nm) (wt %) Kind (wt %) ationation 2A 10 TMAH 0.5 Ammonium 0.3 Colloidal 35, 70 0.9 None — 10.8 10.8Carbonate Silica 2B 10 TMAH 0.3 Ammonium 0.16 Colloidal 15, 25 0.9 None— 10.6 10.5 Nitrate Silica 2C 5 TEAH 0.9 Ammonium 0.8 Colloidal 35, 700.9 None — 10.6 10.4 Carbonate Silica 2D 10 TMAH 0.3 Ammonium 0.16Composit 180 0.5 None — 10.6 10.5 Carbonate Particle 2E 10 TMAH 0.2Ammonium 0.09 Colloidal 35, 70 0.9 Ammonia 0.1 11.0 11.1 CarbonateSilica pH Water Soluble Basic Diluted Diluted Polymer Organic CompoundAbrasive Grain Other Additives 2 hours 90 days Amount Amount ParticleAmount Amount after after Dilution Mixed Mixed Diameter Mixed MixedPrepar- Prepar- Liquid II Slurry Rate Kind (wt %) Kind (wt %) Kind (nm)(wt %) Kind (wt %) ation ation 2a 5 HEC 0.03 Tri- 0.6 Colloidal 35, 700.5 TMAH 0.02  10.1 10.1 ethanolamine Silica 2b 5 HEC 0.1 Di- 1.0Colloidal 15, 25 1.2 None — 10.3 10.2 ethanolamine Silica 2c 10 HEC 0.06Tri- 0.7 Composit 180 0.6 TMAH 0.005 10.2 10.2 ethanolamine Particle 2d5 CMC 0.15 Tri- 0.9 None — — None — 10.6 10.5 ethanolamine

[0289] TABLE 10 pH Additive 1 Additive 2 Abrasive Grain Diluted DilutedAmount Amount Particle Amount 2 hours 90 days Dilution Mixed MixedDiameter Mixed after after Liquid I Slurry Rate Kind (wt %) Kind (wt %)Kind (nm) (wt %) Preparation Preparation 2F 10 TMAH 0.4 HEC 0.3Colloidal 35, 70 0.6 10.3 10.1 Silica 2G 10 KOH 0.5 None — Colloidal 35,70 0.9 12.2 11.5 Silica pH Diluted Additive 3 Additive 4 Abrasive GrainDiluted 3 months Amount Amount Particle Amount 2 hours after DilutionMixed Mixed Diameter Mixed after Prepar- Liquid II Slurry Rate Kind (wt%) Kind (wt %) Kind (nm) (wt %) Preparation ation 2e  5 HEC 0.1 KOH 0.04Colloidal 35, 70 0.5 10.3 10.1 Silica 2f 10 None — Tri- 0.5  Colloidal15, 25 0.6 11.2 11.0 ethanolamine Silica

[0290] Incidentally, in Tables 9 and 10, “Liquid I” and “Liquid II” meanFirst Aqueous Dispersion Material (I) and Second Aqueous DispersionMaterial (II), respectively.

[0291] [4] Evaluation of Polishing Performance on Polysilicon Film:

Example 2-1

[0292] (i) Evaluation of Polishing Rate on Polysilicon Film:

[0293] Aqueous Dispersion [2A] (product diluted after 2 hours form thepreparation) and Aqueous Dispersion [2a] (product diluted after 2 hoursform the preparation) prepared in the step [3] were used to polish apolysilicon film (film thickness: 5,000 Å) on an 8-inch siliconsubstrate having a thermal oxidation film. Specifically, the siliconsubstrate was placed on a chemical mechanical polishing apparatus (Model“EPO112”, manufactured by Ebara Corporation) to polish the polysiliconfilm by means of a polishing pad (product of Rodel Nitta, Ltd.; tradename “IC1000”) made of porous polyurethane under the followingconditions. The respective aqueous dispersions were fed to a platenthrough separate lines. The polishing rate of the polysilicon film wasfound to be 2500 Å/min.

[0294] Carrier load: 300 g/cm²

[0295] Carrier rotating speed: 50 rpm

[0296] Platen rotating speed: 55 rpm

[0297] Feeding rate of slurry 125 ml/min

[0298] Polishing time: 1 minute.

[0299] [ii] Evaluation of Polishing and Removal Selectivity as toPolysilicon Film and Silicon Oxide Film:

[0300] The polishing rate of a silicon oxide film was determined in thesame manner as in the evaluation [i] except that an 8-inch silicon oxidefilm substrate (film thickness: 5,000 Å) was used in place of on the8-inch silicon substrate having a thermal oxidation film in theevaluation [i], and the polishing time was changed to 3 minutes. As aresult, the polishing rate was 6 Å/min. From this fact, the polishingand removal selectivity as to the polysilicon film and the silicon oxidefilm of the two-liquid mixed type slurry composed of a mixture ofAqueous Dispersion [2A] and Aqueous Dispersion [2a] was able to becalculated as 415.

[0301] [iii] Evaluation of Polishing and Removal Selectivity as toPolysilicon Film and Silicon Nitride Film:

[0302] The polishing rate of a silicon nitride film was determined inthe same manner as in the evaluation [i] except that an 8-inch siliconnitride film substrate (film thickness: 1,000 Å) was used in place ofthe 8-inch silicon substrate having a thermal oxidation film in theevaluation [i], and the polishing time was changed to 3 minutes. As aresult, the polishing rate was 5 Å/min. From this fact, the polishingand removal selectivity as to the polysilicon film and the siliconnitride film of the two-liquid mixed type slurry composed of a mixtureof Aqueous Dispersion [2A] and Aqueous Dispersion [2a] was able to becalculated as 500.

[0303] [iv] Evaluation of Erosion:

[0304] A polishing treatment was conducted in the same manner as in theevaluation [i] except that a wafer with polysilicon deposited (amount ofpolisilicon deposited: 3500 Å) on a silicon oxide film including apattern of a wiring 50 μm wide/a non-wiring portion 9 μm wide and apattern of a wiring 2 μm wide/a non-wiring portion 0.35 μm wide was usedin place of the 8-inch silicon substrate having a thermal oxidation filmin the evaluation [i], and the polishing time was set so as to exceed by30% as much as the standard time. After the polishing, erosion at analternate wiring site having the wiring width of 50 μm and an alternatewiring site having the wiring width of 2 μm was measured by means of astep height and surface roughness meter (Model “P-10”, manufactured byKLA-Tencor Co.). As a result, erosion at the alternate wiring sites were510 Å 440 Å, respectively. When these values are not greater than 600 Åand 500 Å, respectively, the erosion resistance may safely be said to begood.

[0305] Incidentally, the polishing time exceeding by 30% as much as thestandard time was calculated in the following manner based on thepolishing rate of the polysilicon film measured in the evaluation [i]and performed.

Polishing time (min)=[Amount of polysilicon deposited (Å)/Polishing rate(Å/min) of polysilicon film]×1.3

[0306] (v) Evaluation of Scratches:

[0307] With respect to the polysilicon films after polished in theevaluation (i), the total number of scratches occurred on the wholesurface of each of the polished surfaces was counted by means of a waferdefect inspection apparatus (Model “KLA2351”, manufactured by KLA-TencorCo.). As a result, one scratch was counted.

[0308] (vi) Evaluation of Stability of High-Concentration Product ofAqueous Dispersion:

[0309] Evaluation as to the respective items was made in substantiallythe same manner as in the evaluation (i) to (v) except that a two-liquidmixed type slurry obtained by diluting High-Concentration Products [2Ad]and [2ad] after stored at 40° C. for 90 days after the preparation wasused in place of the two-liquid mixed type slurry obtained by dilutingHigh-Concentration Products [2Ad] and [2ad] after 2 hours from thepreparation in the evaluation (i) to (v). The results are shown in Table11.

[0310] As apparent from Table 11, it was understood that the performanceof Aqueous Dispersion [2A] and Aqueous Dispersion [2a] is almost thesame between the case where High-Concentration Products [2Ad] and [2ad]were diluted for use after 2 hours from the preparation and the casewhere High-Concentration Products [2Ad] and [2ad] were diluted for useafter stored at 40° C. for 90 days after the preparation, and thus haveexcellent long-term stability in a high-concentration state.

Examples 2-2 to 2-7 and Comparative Examples 2-1 to 2-5

[0311] Evaluation was made in substantially the same manner as inExample 2-1 except that their corresponding first aqueous dispersionmaterial (I) and second aqueous dispersion material (II) shown in Tables11 and 12 were used in place of Aqueous Dispersions [2A] and [2a] inExample 2-1. The results are shown in Tables 11 and 12. TABLE 11 ExampleExample Example Example Example Example Example 2-1 2-2 2-3 2-4 2-5 2-62-7 First Aqueous Dispersion Material (I) 2A 2A 2B 2C 2A 2D 2E SecondAqueous Dispersion Material (II) 2a 2a 2b 2d 2d 2c 2d Mixing Method(I:II) Mixed on Mixed on Mixed by Mixed by Mixed on Mixed by Mixed byTable Table Supply Supply Table Supply Supply Line Line Line Line Ratioof Feeding 125:125 75:175 125:125 175:75 150:150 175:100 125:125 Rate ofSlurry (I:II) Diluted Polishing Rate of 2500 1750 1200 2950 1900 23002200 2 hours Polysilicon after Film (Å/min) Preparation Ratio ofPolishing rate 415 350 240 420 270 460 440 Polysilicon: Silicon OxideRatio of Polishing rate 500 435 300 490 380 575 550 Polysilicon: SiliconNitride Erosion (Å) 510 350 350 550 500 500 400 Wiring Width 50 μmWiring Width 2 μm 440 300 300 500 400 350 350 Scratch (counts/wafer) 1 01 2 0 1 0 Diluted Polishing Rate of 2450 1600 1150 2800 1950 2400 225090 days Polysilicon Film (Å/min) after Ratio of Polishing rate 410 320290 400 280 400 450 Preparation Polysilicon: Silicon Oxide Ratio ofPolishing rate 490 400 290 560 325 600 560 Polysilicon: Silicon NitrideErosion (Å) 450 350 300 600 600 450 400 Wiring Width 50 μm Wiring Width2 μm 400 350 300 450 450 400 350 Scratch (counts/wafer) 1 0 0 3 1 0 0

[0312] TABLE 12 Comparative Comparative Comparative ComparativeComparative Example 2-1 Example 2-2 Example 2-3 Example 2-4 Example 2-5First Aqueous Dispersion Material (I) 2A — 2F 2G 2A Second AqueousDispersion Material (II) — 2a 2e 2f 2e Mixing Method (I:II) Mixed onMixed on Mixed by Mixed by Mixed on Table Table Supply Line Supply LineTable Ratio of Feeding 200:— —:200 125:125 175:75 75:175 Rate of Slurry(I:II) Diluted Polishing Rate of 4250 450 1100 3300 1800 2 hoursPolysilicon Film (Å/min) after Ratio of Polishing rate 850 150 15 660 35Preparation Polysilicon: Silicon Oxide Ratio of Polishing rate 850 22590 825 180 Polysilicon: Silicon Nitride Erosion (Å) 750 350 1000 900 800Wiring Width 50 μm Wiring Width 2 μm 600 300 900 800 700 Scratch(counts/wafer) 30 0 1 50 15 Diluted Polishing Rate of 4100 550 1200 31001850 90 days Polysilicon (Å/min) after Ratio of Polishing rate 820 18015 620 35 Preparation Polysilicon: Silicon Oxide Ratio of Polishing rate910 275 85 775 185 Polysilicon: Silicon Nitride Erosion (Å) 800 350 1050950 850 Wiring Width 50 μm Wiring Width 2 μm 400 300 950 800 700 Scratch(counts/wafer) 45 0 0 45 10

[0313] [5] Evaluation of Polishing Performance on MonocrystallineSilicon Film:

Example 2-8

[0314] (vii) Evaluation of Polishing Rate of Monocrystalline SiliconFilm:

[0315] Aqueous Dispersions [2A] and [2a] (products diluted after 2 hoursform the preparation) prepared in the step [3] were used, and a siliconwafer (product of E & M Co.) was placed on a chemical mechanicalpolishing apparatus (Model “EPO112”, manufactured by Ebara Corporation)to conduct polishing in the same manner as in the step [4](i). Thepolishing rate of the monocrystalline silicon film was 1400 Å/min.

[0316] (viii) Evaluation of Scratches:

[0317] With respect to the silicon wafer after polished in theevaluation (vii), the number of scratches was counted in the same manneras in the evaluation (v). As a result, no scratch was counted.

[0318] (ix) Evaluation of Stability of High-Concentration Product ofAqueous Dispersions:

[0319] Evaluation was carried out in substantially the same manner as inthe evaluation (vii) except that a two-liquid mixed type slurry obtainedby diluting High-Concentration Products [2Ad] and [2ad] after stored at40° C. for 90 days after the preparation was used in place of thetwo-liquid mixed type slurry obtained by diluting High-ConcentrationProducts [2Ad] and [2ad] after 2 hours from the preparation in theevaluation (vii).

[0320] As a result, the polishing rate of the monocrystalline siliconfilm was 1300 Å/min, no scratch was counted, and there was littledifference in polishing performance even when a two-liquid mixed typeslurry obtained by diluting High-Concentration Products [2Ad] and [2ad]after stored at 40° C. for 90 days after the preparation was used.

[0321] [Effect of the Invention]

[0322] The first aqueous dispersion for chemical mechanical polishingaccording to the present invention is excellent in surface planarizingability, hence, occurrence of dishing, erosion or the like in aplarnarizing step of a surface to be polished by chemical mechanicalpolishing is low, and high in shelf stability, therefore preventsdeterioration with time even in storage in a state of a highconcentration and so excellent in long-term stability.

[0323] The first chemical mechanical polishing process according to thepresent invention achieves a high polishing rate when a silicon filmsuch as a polysilicon film is polished, and has excellent selectivitywhen a polysilicon film and a silicon oxide film are polished andremoved and excellent selectivity when a polysilicon film and a nitridefilm are polished and removed.

[0324] The second aqueous dispersion for chemical mechanical polishingaccording to the present invention is excellent in surface planarizingability, hence, occurrence of dishing, erosion or the like in aplarnarizing step of a surface to be polished by chemical mechanicalpolishing is low, does not cause or at least lessens surface defectsincluding scratches, is high in shelf stability, therefore preventsdeterioration with time even in storage in a state of a highconcentration and so excellent in long-term stability.

[0325] In the second aqueous dispersion for chemical mechanicalpolishing according to the present invention, a polishing rate is moreimproved when the water-soluble quaternary ammonium salt is a compoundrepresented by the formula (1).

[0326] When the inorganic acid salt is an inorganic ammonium salt,dishing and erosion can be sufficiently prevented.

[0327] When it is used in polishing of a silicon type film, thepolishing rate is high, and dishing and the like are prevented.

[0328] According to the second chemical mechanical polishing process ofthe present invention, a surface to be polished can be polished at asufficient rate, dishing, erosion and the like can be lessened, andscratches can also be prevented.

[0329] When a ratio of the polishing rate of a polysilicon film to thepolishing rate of a silicon oxide film is at least 30 when polishing isconducted under the same conditions, these films can be polished withsufficient selectivity.

[0330] When a ratio of the polishing rate of a polysilicon film to thepolishing rate of a nitride film is at least 50 when polishing isconducted under the same conditions, these film and layer can bepolished with sufficient selectivity.

[0331] According to the production process of a semiconductor device ofthe present invention, there can be provided semiconductor deviceshaving excellent surface smoothing and high quality.

What is claimed is:
 1. An aqueous dispersion for chemical mechanicalpolishing obtained by mixing a water-soluble quaternary ammonium salt,an inorganic acid salt and abrasive grains into an aqueous medium. 2.The aqueous dispersion for chemical mechanical polishing according toclaim 1, wherein the water-soluble quaternary ammonium salt, inorganicacid salt and abrasive grains are contained in proportions of 0.005 to5% by mass, 0.005 to 5% by mass and 0.01 to 10% by mass, respectively.3. The aqueous dispersion for chemical mechanical polishing according toclaim 1, which further comprises a water-soluble polymer.
 4. The aqueousdispersion for chemical mechanical polishing according to claim 1,wherein the water-soluble quaternary ammonium salt is a compoundrepresented by the following formula (1): [NR₄]⁺[OH]⁻  (1) wherein R isan alkyl group having 1 to 4 carbon atoms.
 5. The aqueous dispersion forchemical mechanical polishing according to claim 1, wherein theinorganic acid salt is an inorganic ammonium salt.
 6. The aqueousdispersion for chemical mechanical polishing according to claim 1, whichis used in polishing of a silicon type film.
 7. A chemical mechanicalpolishing process comprising a step of polishing a surface to bepolished with the aqueous dispersion for chemical mechanical polishingaccording to claim
 1. 8. The chemical mechanical polishing processaccording to claim 7, wherein a first specific removal rate ratiorepresented by a ratio of the removal rate of a polysilicon film to theremoval rate of a silicon oxide film in the case where the silicon oxidefilm and the polysilicon film are polished under the same condition, isat least
 30. 9. The chemical mechanical polishing process according toclaim 7, wherein a second specific removal rate ratio represented by aratio of the removal rate of a polysilicon film to the removal rate of anitride film in the case where the nitride film and the polysilicon filmare polished under the same condition, is at least
 50. 10. A process forproducing a semiconductor device, wherein the semiconductor device isproduced by conducting step of polishing a surface to be polished on asemiconductor substrate with the aqueous dispersion for chemicalmechanical polishing according to claim
 1. 11. An aqueous dispersion forchemical mechanical polishing obtained by mixing at least awater-soluble quaternary ammonium salt, another basic organic compoundthan the water-soluble quaternary ammonium salt, an inorganic acid salt,a water-soluble polymer and abrasive grains into an aqueous medium. 12.The aqueous dispersion for chemical mechanical polishing according toclaim 11, wherein the water-soluble quaternary ammonium salt, anotherbasic organic compound than the water-soluble quaternary ammonium salt,inorganic acid salt, water-soluble polymer and abrasive grains arecontained in proportions of 0.005 to 10% by mass, 0.005 to 10% by mass,0.005 to 8% by mass, 0.001 to 5% by mass and 0.01 to 10% by mass,respectively.
 13. The aqueous dispersion for chemical mechanicalpolishing according to claim 11, wherein the water-soluble quaternaryammonium salt is a compound represented by the following formula (1):[NR₄]⁺[OH]⁻  (1) wherein R is an alkyl group having 1 to 4 carbon atoms.14. The aqueous dispersion for chemical mechanical polishing accordingto claim 11, wherein the inorganic acid salt is an inorganic ammoniumsalt.
 15. The aqueous dispersion for chemical mechanical polishingaccording to claim 11, which is used in polishing of a silicon typefilm.
 16. A chemical mechanical polishing process comprising a step ofpolishing a surface to be polished with the aqueous dispersion forchemical mechanical polishing according to claim
 11. 17. The chemicalmechanical polishing process according to claim 16, wherein a firstspecific removal rate ratio represented by a ratio of the removal rateof a polysilicon film to the removal rate of a silicon oxide film in thecase where the silicon oxide film and the polysilicon film are polishedunder the same condition, is at least
 30. 18. The chemical mechanicalpolishing process according to claim 16, wherein a second specificremoval rate ratio represented by a ratio of the removal rate of apolysilicon film to the removal rate of a nitride film in the case wherethe nitride film and the polysilicon film are polished under the samecondition, is at least
 50. 19. A process for producing a semiconductordevice, wherein the semiconductor device is produced by conducting astep of polishing a surface to be polished on a semiconductor substratewith the aqueous dispersion for chemical mechanical polishing accordingto claim
 11. 20. A material for preparing an aqueous dispersion forchemical mechanical polishing, comprising a first aqueous dispersionmaterial (I) obtained by mixing at least a water-soluble quaternaryammonium salt and an inorganic acid salt into an aqueous medium, and asecond aqueous dispersion material (II) obtained by mixing at least awater-soluble polymer and another basic organic compound than thewater-soluble quaternary ammonium salt into an aqueous medium, whereinabrasive grains are mixed into at least one of the first aqueousdispersion material (I) and the second aqueous dispersion material (II),and the aqueous dispersion for chemical mechanical polishing is preparedby both of the first aqueous dispersion material (I) and the secondaqueous dispersion material (II).
 21. The material for preparing anaqueous dispersion for chemical mechanical polishing according to claim20, wherein the water-soluble quaternary ammonium salt is a compoundrepresented by the following formula (1): [NR₄]⁺[OH]⁻  (1) wherein R isan alkyl group having 1 to 4 carbon atoms.
 22. The material forpreparing an aqueous dispersion for chemical mechanical polishingaccording to claim 20, wherein the ratio [(I)/(II)] of the first aqueousdispersion material (I) to the second aqueous dispersion material (II)is 30/70 to 70/30 in terms of a mass ratio.
 23. The material forpreparing an aqueous dispersion for chemical mechanical polishingaccording to claim 20, wherein the inorganic acid salt is an inorganicammonium salt.